Fluid-assisted medical devices, systems and methods

ABSTRACT

Surgical devices, systems and methods for treating tissue are provided. An exemplary surgical device comprises a tip portion including first and second jaws each having a tissue grasping surface, at least one of the jaws being movable toward the other jaw. The tissue grasping surface of each jaw has includes an electrically insulative surface. The device also includes first and second electrodes connectable to different terminals of an RF generator to generate electrical current flow therebetween, with each of the electrodes having an electrode surface. One of the electrode surfaces is located on one of the jaws separated from one edge of the tissue grasping surface, and the other of the electrode surfaces is located on one or the other of the jaws separated from the other edge of the tissue grasping surface. The device also includes at least one fluid passage being connectable to a fluid source.

This application is being filed as a PCT International Patentapplication in the name of TissueLink Medical, Inc. (a U.S. nationalcorporation), for the designation of all countries except the U.S., andMichael E. McClurken, David Lipson, Arnold E. Oyola and David Flanagan(all U.S. citizens), for the designation of the US only, on May 15,2003.

FIELD

This invention relates generally to the field of medical devices,systems and methods for use upon a body during surgery. Moreparticularly, the invention relates to electrosurgical devices, systemsand methods for use upon tissues of a human body during surgery,particularly open surgery and minimally invasive surgery such aslaparoscopic surgery.

BACKGROUND

The application of heat to tissue, typically from a flame heated metalobject, has been used for centuries to cauterize bleeding wounds. Incauterization, the essential mechanism behind tissue treatment involvesraising the temperature of the bleeding tissue by conductive heattransfer from the heated metal object. In order to arrest bleeding fromthe tissue's severed blood vessels, the tissue is heated adequately toshrink certain tissue proteins, such as collagen, thus closing the bloodvessels and ultimately leading to blood vessel thrombosis.

Apart from shrinkage, the application of compressive force from a heatedmetal object to a blood vessel may also result in collagen welding, suchas for the permanent joining together of opposite walls of a bloodvessel, thus providing another mechanism of hemostasis in addition tosimple shrinkage of collagen.

With the aid of electricity, cauterization spurred the development ofelectrocautery devices to treat bleeding. While electrocautery devicesstill involve the use of a heated metal object, the electrocauterydevice is heated via electrical energy converted to heat in the metalobject as opposed to heating the metal with a direct flame.

More recently, coagulation may be accomplished by radio frequency (“RF”)electrosurgical devices where electrical energy is converted to heat inthe tissue rather than in the device. Heating of the tissue is oftenperformed by means of resistance heating. In other words, increasing thetemperature of the tissue as a result of electric current flow throughthe tissue which is resisted by the tissue. Electrical energy isconverted into thermal energy (i.e. heat) via accelerated movement ofions as a function of the tissue's electrical resistance and currentflow.

Hemostasis of the above sort is not without its drawbacks. Current drytip RF electrosurgical devices can cause the temperature of tissue beingtreated to rise significantly higher than 100° C., thus exceeding theboiling temperature of inter-cellular water and resulting in tissuedesiccation, tissue sticking to the electrodes, tissue perforation, charformation and smoke generation. Peak tissue temperatures at a targetedtissue treatment site can be as high as 320° C. as a result of RFtreatment, and such high temperatures can be transmitted to adjacentuntargeted-tissue via conduction. Undesirable results of suchtransmission to untargeted adjacent tissue include unintended thermaldamage to the untargeted tissue.

According to U.S. Pat. No. 6,086,586 to Hooven entitled “Bipolar TissueGrasping Apparatus and Tissue Welding Method”, currently-availablebipolar grasping instruments for electro-coagulation of tissue, or“tissue welding,” generally use only two electrodes of oppositepolarity, one of which is located on each of the opposite jaws of thegrasper. As illustrated in Hooven's FIG. 1, in use, tissue is heldbetween a pair of grasper jaws (shown in cross-section) having first andsecond electrodes (Electrode 1 and Electrode 2) of opposite polarity.Bipolar current flows between the two electrodes along the illustratedcurrent flow lines, with tissue coagulating first at the edges of thejaws. Then, as the tissue dries out and the impedance increases, thecurrent flows through the moister tissue and the coagulation spreadsboth inward toward the center of the jaws and outward from the jawedges.

The Hooven patent goes on to recite that “[t]hermal damage to adjacentstructures can occur due to this spread of thermal energy outside thejaws of the instrument. Because of the spread of thermal energy outsidethe jaws of the instrument, it is difficult to coagulate long sectionsof tissue, such as bowel, lung, or larger blood vessels, withoutsignificant lateral thermal spread. Over-coagulation frequently occurs,resulting in tissue sticking to the jaws of the instrument. When thejaws of the instrument are opened, if the tissue sticking is severe, thetissue can be pulled apart, thus adversely affecting hemostasis.”

As part of the summary of the invention, the Hooven patent recites “abipolar electrosurgical instrument having a pair of relatively moveablejaws, each of which includes a tissue contacting surface. The tissuecontacting surfaces of the jaws are in face-to-face relation with oneanother, and adjacent each of the tissue contacting surfaces are firstand second spaced-apart electrodes that are adapted for connection tothe opposite terminals of a bipolar RF generator so as to generate acurrent flow therebetween.” Furthermore, the Hooven patent recites that,“[b]ecause each jaw is a bipolar electrode, multiple local currentpathways, high current densities, and lower impedances are achieved.Indeed, the maximum current density is between the two insulated jawsurfaces, while a relatively lower current density exists at theelectrode surfaces.”

However, the invention of the Hooven patent encounters certaindifficulties. Due to tissue irregularities, the surface of the tissue tobe treated may be uneven or undulated with peaks and valleys.Consequently, the area of electrical coupling of the tissue to theelectrode surfaces can be limited to the isolated peaks in the tissuesurface. In this situation, upon the application of RF power to tissue,the electrical coupling of only the tissue peaks to the electrodesurfaces may result in corresponding increase in current density throughthe electrically coupled peaks which has the ability to desiccate andchar the tissue at these isolated locations. Hooven does not address orprovide for this situation.

Another difficulty encountered with the Hooven invention is that it doesnot address or provide for a decreasing electrical coupling between thetissue and electrode surfaces upon tissue shrinkage and/or desiccationduring treatment. As tissue shrinks and/or desiccates during treatment,the tissue surfaces may loose contact with the electrode surfaces which,similar to above, decreases the area of electrical coupling therebetweenand correspondingly increases the current density and associated heat atthe locations which remain electrically coupled. This difficulty isfurther exacerbated if the tissue is undulated as described above.

Another difficulty encountered with the Hooven invention is that it doesnot address or provide for dissipating heat from the insulating members.Hooven does not address or provide how heat which may be conducted intothe insulating members from the tissue between the two insulatedsurfaces is subsequently removed from the insulating members.

In light of the above, it is an object of the invention to providedevices, systems and methods which overcome the limitations of the art.

SUMMARY OF THE INVENTION

The present invention provides devices, systems and methods thatinhibit, and more preferably minimize or prevent, tissue necrosisoutside a targeted tissue treatment site during a medical procedure. Theinvention is particularly useful during surgical procedures upon tissuesof a human body, where it is desirable to coagulate and shrink tissue,to occlude lumens of blood vessels (e.g. arteries, veins), airways (e.g.bronchi, bronchioles), bile ducts and lymphatic ducts.

According to the present invention, electrosurgical devices, systems andmethods are provided in which the electrical current paths, associatedelectrical resistance heating and ensuing thermal conduction heating aresubstantially limited to tissue within the jaws of the device, so as toinhibit, and preferably prevent, tissue damage outside the jaws due tothermal effects. More preferably, the electrical current paths, as wellas current density, are concentrated within the confines and borders oftwo electrically insulated surfaces of the jaws and, even morepreferably, within the medial portions of the electrically insulatedsurfaces.

According to the present invention, electrosurgical devices, systems andmethods are provided in which the maximum current density and heating oftissue (by both electrical resistance heating and thermal conductionheating) occurs apart or removed from the electrodes and preferablybetween the two electrically insulated surfaces. More preferably, theelectrodes are configured such that the portion of the electrodesurfaces closest to the two electrically insulated surfaces is remotelylocated and separated from the electrically insulated surfaces.

According to the present invention, electrosurgical devices, systems andmethods are provided in which the electrical coupling between tissue andthe electrodes is enhanced, so as to inhibit tissue damage outside theelectrically insulated surfaces, particularly to tissue nearest theelectrodes. Tissue damage can be manifest in many ways, depending on thetissue temperature encountered, ranging from coagulation necrosis attemperatures from 50 to 100° C., to sticking at temperatures above 120°C., to charring, arcing and smoke formation at temperatures exceeding200° C.

According to the present invention, preferably the enhanced electricalcoupling is provided by an electrically conductive fluid which couplesbetween the tissue surface and the electrodes and increases theuniformity of the electrical coupling therebetween. In addition toinhibiting tissue damage as outlined above, this enhancement isparticularly useful to counter poor electrical coupling associated withprior art dry devices, uneven and undulated tissue, shrinkage of treatedtissue, desiccation of treated tissue and motion of the jaws whilegrasping tissue.

According to the present invention, electrosurgical devices, systems andmethods are provided in which a portion of the electrical current, uponexiting from between the two electrically insulated surfaces, flows atleast partially through the electrically conductive fluid, rather thanthrough the tissue outside the electrically insulated surfaces, beforereaching the counter electrode. According to the present invention, thiswill inhibit tissue damage outside the electrically insulated surfacesgiven the decrease in electrical current through the tissue andassociated decrease in power in the tissue will correspondingly reducethe amount of resistance and conduction heating of the tissue.

According to the present invention, electrosurgical devices, systems andmethods are provided and configured to provide a diversion andpreferably divert at least a portion of the electrical current, uponexiting from between the two electrically insulated surfaces, at leastpartially through the conductive fluid before reaching the counterelectrode. Preferably at least a portion of the electrically conductivefluid coupling the electrodes and the tissue outside the electricallyinsulated surfaces electrical couples tissue adjacent the electricallyinsulated surfaces. Also, preferably, at least a portion of theelectrically conductive fluid coupling the electrodes and the tissueadjacent the electrically insulated surfaces electrical couples thetissue and the electrodes at the shortest distance there between.

Preferably the electrosurgical devices, systems and methods areconfigured such that the electrical current exiting from between the twoelectrically insulated surfaces will be more apt to be concentrated andflow at least partially through the electrically conductive fluid,rather than through the tissue outside the electrically insulatedsurfaces, to the counter electrode.

Preferably the electrically conductive fluid is provided in aconfiguration to present an electrical resistance to the electricalcurrent exiting from between the two electrically insulated surfaceswhich is less than the electrical resistance encountered in tissueoutside the electrically insulated surfaces. Preferably the electricallyconductive fluid has an electrical resistivity less than the electricalresistivity of the tissue through which electrical current would flow inthe absence of the electrically conductive fluid prior to treatment withthe device.

According to the present invention, the source electrode side relativeto the tissue grasping surfaces is configured similar to the counterelectrode side. As electrical current flows from the source electrodeand enters between the tissue grasping surfaces it will also seek a pathto the counter electrode comprising the least electrical resistance.Consequently, in addition to the above, the device is also configured toprovide a diversion for and preferably divert at least a portion of theelectrical current, upon leaving the source electrode, at leastpartially through the conductive fluid before entering between thegrasping surfaces.

Preferably the electrically conductive fluid is provided to tissue bymeans of the electrosurgical device. Also preferably, the electricallyconductive fluid comprises a saline solution. Furthermore, in certainembodiments, the saline solution may comprise physiologic saline orhypertonic saline.

According to the present invention, electrosurgical devices, systems andmethods are provided in which removal of heat from and cooling of thetissue outside the electrically insulated surfaces is enhanced, so as toinhibit tissue damage outside the electrically insulated surfaces.Preferably, the enhanced cooling is provided by a fluid, particularlythe electrically conductive fluid. More particularly, in the event aportion of the electrical current exiting from between the twoelectrically insulated surfaces flows through tissue outside theelectrically insulated surfaces, thus heating the tissue outside theelectrically insulated surfaces by resistance and conduction heating,the conductive fluid function as a heat sink to absorb and remove heatfrom the tissue and cool the tissue. Furthermore, it is an object of thepresent invention that the conductive fluid lubricates thetissue/electrode interface and the tissue/electrically insulated surfaceinterface as to inhibit sticking thereto.

According to the present invention, electrosurgical devices, systems andmethods are provided which are configured to remove heat from and coolthe Jaws, particularly the electrically insulated surfaces of the jaws,and more particularly the medial portion of the insulated surfaces. Insome embodiments, the electrically insulated surfaces of the jawscomprise or are supported by a material with a high thermalconductivity. In other embodiments, heat is removed from the jaws by theelectrically conductive fluid.

According to the present invention, electrosurgical devices, systems andmethods are provided for medical procedures, which preferably utilizeradio frequency (“RF”) power and electrically conductive fluid duringthe treatment of tissue. Preferably, the temperature of the tissue,particularly outside a targeted tissue treatment site (e.g. outside theelectrically insulated surfaces of the jaws), may be altered and atleast partially controlled (e.g. maintained within a targetedtemperature range or at a targeted tissue temperature) by adjustingparameters (e.g. the fluid flow rate of the electrically conductivefluid) that affect the temperature of the tissue.

According to the present invention, using a fluid in the above mannerinhibits, and preferably minimizes or prevents tissue damage (e.g.necrosis), and such undesirable effects as tissue sticking toelectrodes, smoke generation, char formation and desiccation, to tissueoutside a targeted tissue treatment site.

According to the present invention, a tissue grasping device is providedcomprising a tip portion including a first jaw and a second jaw with atleast one of the jaws being movable toward the other jaw. The first jawincludes a first tissue grasping surface and the second jaw includes asecond tissue grasping surface. The tissue grasping surface of each jawhas a length defined by proximal and distal ends, a width defined byedges and further comprises an electrically insulative surface. Thedevice further comprises first and second electrodes being connectableto different terminals of a radio frequency generator to generateelectrical current flow therebetween, with the first electrode having afirst electrode surface and the second electrode having a secondelectrode surface. One of the first and second electrode surfaces islocated on one or the other of the jaws separated from one edge of thetissue grasping surface and the other of the electrode surfaces islocated on one or the other of the jaws separated from the other edge ofthe tissue grasping surface. The device also includes at least one fluidpassage being connectable to a fluid source.

According to the present invention, a device is provided with a tipportion configured to provide radio frequency power from a radiofrequency generator with a fluid from a fluid source to tissue, with thefluid provided to the tissue at a tissue surface and the radio frequencypower provided to the tissue below the tissue surface.

According to another aspect of the present invention, a device isprovided with a tip portion configured to provide radio frequency powerto tissue at least partially through a fluid coupling located on asurface of the tissue, with the fluid coupling comprising anelectrically conductive fluid provided from a fluid source and theelectrically conductive fluid provided from the tip portion with theradio frequency power.

According to another aspect of the invention, a device is provided thatis configured to receive radio frequency power from a radio frequencygenerator at a power level and an electrically conductive fluid from afluid source at a fluid flow rate, and deliver the electricallyconductive fluid to tissue at a tissue surface and the radio frequencypower to the tissue below the tissue surface.

According to yet another aspect to the invention, a device is providedthat is configured to receive radio frequency power from a radiofrequency generator at a power level and an electrically conductivefluid from a fluid source at a fluid flow rate, and deliver theelectrically conductive fluid to tissue at a tissue surface and theradio frequency power to the tissue below the tissue surface at leastpartially through a fluid coupling comprising the electricallyconductive fluid.

In certain embodiments, the tip portion further comprises at least onefluid outlet in fluid communication with a fluid passage configured toprovide a fluid from a fluid source to tissue. Preferably, the at leastone fluid outlet in fluid communication with the fluid passage furthercomprises a first fluid outlet and a second fluid outlet with the firstfluid outlet being located on the same jaw as a first electrode and thesecond fluid outlet being located on the same jaw as a second electrode.Preferably, the first fluid outlet and the second fluid outlet areconfigured to receive the fluid from the fluid source and provide thefluid to tissue located outside of tissue grasping surfaces.

In one embodiment, a first fluid outlet and a second fluid outlet areconfigured to receive a fluid from a fluid source and provide the fluidto tissue located outside of and adjacent tissue grasping surfaces.

In another embodiment, a first fluid outlet and a second fluid outletare configured to receive a fluid from a fluid source and provide thefluid to tissue located outside of and separated from tissue graspingsurfaces.

In another embodiment, a first fluid outlet is configured to provide afluid to tissue located adjacent a first electrode surface, and a secondfluid outlet is configured to provide a fluid to tissue located adjacenta second electrode surface.

In another embodiment, a first fluid outlet is configured to provide afluid between a first electrode surface and tissue, and a second fluidoutlet is configured to provide a fluid between a second electrodesurface and tissue.

In another embodiment, a first fluid outlet is configured to provide afluid between a first electrode surface and one edge of one or the otherof two tissue grasping surfaces, and a second fluid outlet is configuredto provide a fluid between a second electrode surface and the other edgeof one or the other of the tissue grasping surfaces.

In another embodiment, a first fluid outlet is configured to provide afluid to the first electrode surface, and a second fluid outlet isconfigured to provide a fluid to a second electrode surface.

In another embodiment, a first fluid outlet is configured to provide afluid to a first portion of one or the other of two jaws outside atissue grasping surface, and a second fluid outlet is configured toprovide a fluid to a second portion of one or the other of the jawsoutside a tissue grasping surface.

In one embodiment, each of two first and second electrode surfaces isseparated from a tissue grasping surface of a jaw to which it is locatedby a gap. In another embodiment, at least a portion of each gapseparating each of the first and second electrode surfaces from thetissue grasping surface of the jaw to which it is located is configuredto receive a fluid from a fluid source. In another embodiment, the fluidreceived by each of the gaps is configured to provide a fluid couplingwhich provides cooling and removing heat from tissue located outside thetissue grasping surfaces. In yet another embodiment, the fluid comprisesan electrically conductive fluid, and the fluid received by each of thegaps is configured to provide a fluid coupling which enhances theelectrical connection of the first and second electrode surfaces andtissue located outside the tissue grasping surfaces. Furthermore, in yetanother embodiment, at least a portion of the electrical current flowbetween the first and second electrode surfaces may be caused to flow atleast partially through at least one fluid coupling as opposed to tissuelocated outside the tissue grasping surfaces, whereby the amount ofcurrent flow through tissue located outside the tissue grasping surfacesmay be correspondingly reduced. In one embodiment, the tissue graspingsurface of each jaw has a length, and each gap further comprises anelongated gap separating each of the first and second electrode surfacesfrom the tissue grasping surface of the jaw to which it is located alongthe length of the tissue grasping surface. In another embodiment, atleast a portion of each elongated gap separating each of the first andsecond electrode surfaces from the tissue grasping surface of the jaw towhich it is located is configured to receive a fluid from the fluidsource and provide a fluid flow channel for the fluid along the lengthof the tissue grasping surface.

In yet another embodiment, at least one jaw comprises at least onestand-off configured to keep tissue from physically contacting at leastone of a first electrode surface and a second electrode surface. Invarious embodiments, the stand-off preferably comprises a coil wrappedaround at least a portion of one of the first and second electrodesurface, a material porous to a fluid provided from a fluid source therethrough with the material overlying at least a portion of one of thefirst and second electrode surface, or a foam material overlying atleast a portion of one of the first and second electrode surface. Inother embodiments, the stand-off comprises a polymer or ceramicmaterial.

In other embodiments, at least one jaw comprises at least oneobstruction configured to inhibit a fluid shunt from forming between thefirst electrode and the second electrode. In various embodiments, theobstruction comprises a tissue grasping surface of a jaw, a distal endportion of a jaw, a proximal end portion of a jaw or a backside portionof a jaw, such as a protrusion or recess which provides a drip edge.

In other embodiments, a tissue treatment indicator is provided whichprovides an output related to a level of treatment of tissue. In certainembodiments, the tissue treatment indicator comprises a bulb or athermochromic device wired in parallel with an electrode.

According to another aspect of the invention, a tissue grasping deviceis provided comprising a tip portion including a first jaw and a secondjaw with at least one of the jaws being movable toward the other jaw.Each jaw includes a left-side portion, a right-side portion and a tissuegrasping surface with the tissue grasping surface of each jaw furthercomprising an electrically insulative surface. The device furthercomprises first and second electrodes being connectable to differentterminals of a radio frequency generator to generate electrical currentflow therebetween with the first electrode having a first electrodesurface and the second electrode having a second electrode surface. Oneof the first and second electrodes is located on one or the other of thejaws on the left-side portion of the jaw and the other of the electrodesis located on one or the other of the jaws on the right-side portion ofthe jaw. Each of the first and second electrode surfaces is separatedfrom the tissue grasping surface of the jaw on which it is located. Thedevice also includes at least one fluid passage being connectable to afluid source.

According to another aspect of the invention, a tissue grasping deviceis provided comprising a tip portion including a first jaw and a secondjaw with at least one of the jaws being movable toward the other jaw.Each jaw includes a tissue grasping surface with the tissue graspingsurface of each jaw further comprising an electrically insulativesurface. A portion of each tissue grasping surface is located on eachside of a center plane. The center plane is orientated longitudinal andto the tissue grasping surface. The device further comprises first andsecond electrodes being connectable to different terminals of a radiofrequency generator to generate electrical current flow therebetweenwith the first electrode having a first electrode surface and the secondelectrode having a second electrode surface. One of the first and secondelectrodes is located on one or the other of the jaws on one side of thecenter plane and the other of the electrodes is located on one or theother of the jaws on the other side of the center plane. Each of thefirst and second electrode surfaces is separated from the tissuegrasping surface of the jaw to which it is located. The device alsoincludes at least one fluid passage being connectable to a fluid source.

According to another aspect of the invention, a tissue grasping deviceis provided comprising a tip portion including a first jaw and a secondjaw with at least one of the jaws being movable toward the other jaw.Each jaw includes a tissue grasping surface with the tissue graspingsurface of each jaw further comprising an electrically insulativesurface. A portion of each tissue grasping surface is located on twoopposing sides of a cutting mechanism, the cutting mechanism comprisinga blade. The device further comprises first and second electrodes beingconnectable to different terminals of a radio frequency generator togenerate electrical current flow therebetween with the first electrodehaving a first electrode surface and the second electrode having asecond electrode surface. One of the first and second electrodes islocated on one or the other of the jaws on one side of the cuttingmechanism and the other of the electrodes is located on one or the otherof the jaws on the other side of the cutting mechanism. Each the firstand second electrode surfaces is separated from the tissue graspingsurface of the jaw to which it is located. The device also includes atleast one fluid passage being connectable to a fluid source.

According to another aspect of the invention, a tissue grasping deviceis provided comprising a tip portion including a first jaw and a secondjaw with at least one of the jaws being movable toward the other jaw.Each jaw includes a tissue grasping surface with the tissue graspingsurface of each jaw further comprising an electrically insulativesurface. The device further comprises at least two spaced-apartelectrode surfaces separated from the tissue grasping surface of eachjaw, with the two electrode surfaces on the first jaw in direct opposedrelation with the two electrode surfaces on the second jaw, the opposingelectrode surfaces being of like polarity and the electrode surfaces ofeach jaw being connectable to a power source for providing electricalcurrent flow therebetween. The device also includes at least one fluidpassage being connectable to a fluid source.

According to another aspect of the invention, a method of treatingtissue is provided comprising providing tissue; providing electricalcurrent; providing a fluid; providing a first tissue grasping surfaceand a second tissue grasping surface; grasping a first portion of tissuewith the first portion of tissue located between the tissue graspingsurfaces; providing the fluid to a second portion of tissue with thesecond portion of tissue located outside the tissue grasping surfaces;providing the electric current to the tissue; and directing the electriccurrent in the first portion of tissue to flow across the tissuegrasping surfaces. In certain embodiments, the method further comprisesthe step of cooling the second portion of tissue with the fluid and/orcooling the first portion of tissue with the fluid. Furthermore, incertain embodiments, the step of providing a fluid further comprisesproviding an electrically conductive fluid, and the method includes theadditional step of reducing the electrical current in the second portionof tissue with the fluid.

According to another aspect of the invention, a method of treatingtissue is provided comprising providing tissue; providing electricalcurrent; providing a fluid; providing a first tissue grasping surfaceand a second tissue grasping surface; grasping a first portion oftissue, the first portion of tissue located between the tissue graspingsurfaces; providing the fluid to a second portion of tissue, the secondportion of tissue located outside the tissue grasping surfaces;providing the electric current to the tissue; and directing the electriccurrent in the first portion of tissue to flow substantially parallel tothe tissue grasping surfaces. In certain embodiments, the method furthercomprises the step of cooling the second portion of tissue with thefluid and/or cooling the first portion of tissue with the fluid.Furthermore, in certain embodiments, the step of providing a fluidfurther comprises providing an electrically conductive fluid, and themethod includes the additional step of reducing the electrical currentin the second portion of tissue with the fluid.

According to another aspect of the present invention, a tissue graspingdevice is provided comprising a tip portion including a first jaw and asecond jaw with at least one of the jaws being movable toward the otherjaw. Each jaw includes a tissue grasping surface with the tissuegrasping surface of each jaw further comprising an electricallyinsulative surface. The device further comprises at least two electrodesseparated by the tissue grasping surfaces and located between the twoelectrodes with the two electrodes being connectable to differentterminals of a radio frequency generator to generate electrical currentflow therebetween. The device also includes at least one fluid passagebeing connectable to a fluid source.

According to another aspect of the invention, a tissue grasping deviceof the present invention may be provided with at least one electricaltransformer coupled to the first and second electrodes. In variousembodiments, the transformer may further comprise a voltage transformer,an impedance transformer, an autotransformer, a single coil transformer,a transformer having a first coil electrically insulated from a secondcoil or a step-up transformer. In another embodiment, the at least oneelectrical transformer may further comprise a first transformer and asecond transformer coupled in series to the first and second electrodes,with the first transformer comprising an impedance transformer and thesecond transformer comprising an autotransformer.

The invention is also directed to various embodiments of an adaptor forelectrically coupling between an electrosurgical generator and a bipolarelectrosurgical device. In one embodiment, the adaptor comprises a powerinput connector for coupling the adaptor with a monopolar mode poweroutput connector of the electrosurgical generator, a ground connectorfor coupling the adaptor with a ground connector of the electrosurgicalgenerator, a first and a second power output connector, each forcoupling the adaptor with a first and a second bipolar mode power inputconnector of the bipolar electrosurgical device, respectively, and atleast one electrical transformer coupled between the power inputconnector and the first and second power output connectors with thetransformer comprising an autotransformer. In various embodiments, theadaptor may further comprise a monopolar hand switch connector forcoupling the adaptor with a monopolar mode hand switch connector of theelectrosurgical generator, and at least one bipolar mode hand switchconnector for coupling the adaptor with a bipolar mode hand switchconnector of the electrosurgical device. In other embodiments, theadaptor may further comprise a first and a second bipolar mode handswitch connector for coupling the adaptor with a first and a secondbipolar mode hand switch connector of the electrosurgical device,respectively. Moreover, in other embodiments, the first bipolar modehand switch connector is coupled to the monopolar hand switch connector,and the second bipolar mode hand switch connector is coupled to thepower input connector in parallel with the transformer, whereby thecoupling bypasses the transformer.

In other embodiments, the adaptor may comprise a pair of bipolar powerinput connectors for coupling the adaptor with a pair of bipolar poweroutput connectors of the electrosurgical generator, a pair of bipolarpower output connectors for coupling the adaptor with a pair of bipolarpower input connectors of the bipolar electrosurgical device; and atleast one electrical transformer coupled between the bipolar power inputconnectors and the bipolar power output connectors. In variousembodiments, the adaptor may further comprise a first electricaltransformer and a second electrical transformer coupled in series andbetween the power input connector and the first and second power outputconnectors, with the first transformer comprising an impedancetransformer and the second transformer comprising an autotransformer. Inother embodiments, the adaptor may comprise a bipolar hand switch inputconnector for coupling the adaptor with a bipolar hand switch outputconnector of the electrosurgical generator, and at least one bipolarmode hand switch output connector for coupling the adaptor with abipolar mode hand switch input connector of the electrosurgical device.In still other embodiments, the adaptor may further comprise a first anda second bipolar mode hand switch output connector for coupling theadaptor with a first and a second bipolar mode hand switch inputconnector of the electrosurgical device, respectively. Moreover, instill other embodiments, the first bipolar mode hand switch outputconnector is coupled to the bipolar hand switch input connector, and thesecond bipolar mode hand switch output connector is coupled to one ofthe bipolar power input connectors in parallel with the impedancetransformer and the autotransformer, whereby the coupling bypasses thetransformers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of an exemplary device according to the presentinvention;

FIG. 2 is a top view of the device of FIG. 1;

FIG. 3 is a close-up first side view of the tip portion of the device ofFIG. 1;

FIG. 4 is a close-up second side view of the tip portion of the deviceof FIG. 1;

FIG. 5 is a close-up top view of the tip portion of the device of FIG. 1with jaw 16 a removed;

FIG. 6 is a cross-sectional view of the jaws 16 a, 16 b of the device ofFIG. 1 taken along line 5-5 of FIG. 5;

FIG. 7 is a cross-sectional view of the jaws 16 a, 16 b of the device ofFIG. 1 with tissue and fluid taken along line 5-5 of FIG. 5;

FIG. 8 is a cross-sectional view of an alternative embodiment of jaws 16a, 16 b of the device of FIG. 1 taken along line 5-5 of FIG. 5;

FIG. 9 is an exemplary block diagram showing one embodiment of a systemof the invention with the device of FIG. 1;

FIG. 10 is another cross-sectional view of the jaws 16 a, 16 b of thedevice of FIG. 1 with tissue and fluid taken along line 5-5 of FIG. 5;

FIG. 11 is an exemplary graph that describes the relationship of loadimpedance (Z, in ohms) and generator output power (P, in watts), for anexemplary generator output of 75 watts in a bipolar mode;

FIG. 12 is a cross-sectional view of another alternative embodiment ofjaws 16 a, 16 b of the device of FIG. 1 taken along line 5-5 of FIG. 5;

FIG. 13 is a close-up top view of the alternative embodiment of jaws 16a, 16 b of FIG. 12 with jaw 16 a removed;

FIG. 14 is a cross-sectional view of another alternative embodiment ofjaws 16 a, 16 b of the device of FIG. 1 taken along line 5-5 of FIG. 5;

FIG. 15 is an exemplary graph that describes a relationship between RFpower to tissue (P) versus flow rate of fluid (Q);

FIG. 16 is a cross-sectional view of another alternative embodiment ofjaws 16 a, 16 b of the device of FIG. 1 taken along line 5-5 of FIG. 5;

FIG. 17 is a cross-sectional view of another alternative embodiment ofjaws 16 a, 16 b of the device of FIG. 1 taken along line 5-5 of FIG. 5;

FIG. 18 is an assembled isometric view of another alternative embodimentof the tip portion and jaws 16 a, 16 b of the device of FIG. 1;

FIG. 19 is an exploded isometric view of the assembly of FIG. 18;

FIG. 20 is a first side cross-sectional view of the tip portion of FIG.18;

FIG. 21 is a second side cross-sectional view of the tip portion of FIG.18;

FIG. 22 is an isometric view of another exemplary device according tothe present invention;

FIG. 23 is a block diagram showing another embodiment of a system of theinvention with a device of the present invention;

FIG. 24 is a block diagram of an electrical configuration for agenerator and a device of the present invention without a hand switch;

FIG. 25 is a block diagram of an electrical configuration for agenerator and a device of the present invention with a hand switch;

FIG. 26 is a block diagram of an electrical configuration for agenerator, a device of the present invention with a hand switch, and anadaptor of the present invention therebetween;

FIG. 27 is a block diagram of another electrical configuration for agenerator and a device of the present invention without a hand switch;

FIG. 28 is a block diagram of another electrical configuration for agenerator and a device of the present invention with a hand switch;

FIG. 29 is a block diagram of another electrical configuration for agenerator and a device of the present invention without a hand switch;

FIG. 30 is a block diagram of another electrical configuration for agenerator, a device of the present invention without a hand switch, andan adaptor of the present invention therebetween; and

FIG. 31 is a block diagram of another electrical configuration for agenerator, a device of the present invention with a hand switch, and anadaptor of the present invention therebetween.

DETAILED DESCRIPTION

Throughout the present description, like reference numerals and lettersindicate corresponding structure throughout the several views, and suchcorresponding structure need not be separately discussed. Furthermore,any particular feature(s) of a particular exemplary embodiment may beequally applied to any other exemplary embodiment(s) of thisspecification as suitable. In other words, features between the variousexemplary embodiments described herein are interchangeable as suitable,and not exclusive. Also, from the specification, it should be clear thatany use of the terms “distal” and “proximal” are made in reference tothe user of the device, and not the patient.

An exemplary electrosurgical device according to the present inventionwill now be described in detail. The electrosurgical device may be usedwith the system of the invention to be described herein. However, itshould be understood that the description of the combination is forpurposes of illustrating the system of the invention only. Consequently,it should be understood that the electrosurgical device of the presentinvention can be used alone, or in conjunction with, the system of theinvention. Conversely, it should be equally understood that the systemof the present invention can be used with a wide variety of devices.

An exemplary electrosurgical device of the present invention, which maybe used in conjunction with one or more aspects of the system of thepresent invention, is shown at reference character 10 in FIG. 1. FIG. 1shows a side view of device 10, which is designed and configured tomanipulate (e.g. grasp, coagulate and cut) tissue. Device 10 preferablycomprises a tissue grasper, particularly forceps and more particularlyendoscopic forceps as shown. When device 10 comprises endoscopicforceps, preferably device 10 is configured to extend through a workingchannel of a trocar cannula.

As shown in FIG. 1, device 10 preferably includes an intermediateportion, comprising a hollow shaft 12, and a tip portion 14. As shown,tip portion 14 preferably comprises two directly opposing, cooperating,relatively moveable jaws 16 a, 16 b connected and located adjacent thedistal end 18 of the shaft 12.

Also as shown in FIG. 1, device 10 also preferably includes a collar 20for rotating the entire shaft 12 and connecting a proximal handle 22 tothe proximal end of the shaft 12 and an actuation lever 24 (preferablycomprising a first-class lever) which when squeezed towards the pistolor hand grip portion 26 of the handle 22 in the direction of arrow 28will close the opposing jaws 16 a, 16 b in a manner known in the art.

Continuing with FIG. 1, device 10 also preferably includes a pair ofopposing paddles 30 to activate a built-in cutting mechanism 32 (shownin FIG. 5); a cable 34 extending from the butt of the grip portion 26 ofhandle 22 comprising two insulated wires 36, 38 containing wireconductors 40, 42 (shown in FIGS. 3 and 4) connected and configured todeliver energy (e.g. RF power) to jaws 16 a, 16 b, preferably throughthe shaft 12 and handle 22, and connectable to a source of energy (e.g.via plug connectors to plug clip receptacles 137 a, 137 b of theopposite terminals of a bipolar electrical generator 136 as shown inFIG. 9); and a input fluid line 44 comprising a passage 46 (e.g. lumen)extending from the butt of the grip portion 26 of handle 22 that isconnected and configured to deliver fluid 128 (also shown in FIG. 9) viadividing branches to jaws 16 a, 16 b, also preferably through the shaft12 and handle 22, and connectable to a fluid source 130 (e.g. saline IVbag shown in FIG. 9).

As shown in FIGS. 3 and 4, jaws 16 a, 16 b are preferably connected toan actuator comprising rods 48 which move distally to close the jaws 16a, 16 b with the movement of actuation lever 24 towards grip portion 26of handle 22, and proximally with the opening of the jaws 16 a, 16 bwith the movement of actuation lever 24 away from grip portion 26 ofhandle 22. More specifically, rods 48 preferably extend into movingpivot holes 50, with the rotation for each moving pivot hole 50configured around a hinge comprising a fixed pin 53 extending through afixed pivot hole 52 of shaft 12 and aligning holes in the jaws 16 a, 16b.

Before continuing with the description of jaws 16 a, 16 b, it should beunderstood that, as used herein, the longitudinal dimension is relativeto the length of the jaws 16 a, 16 b and is directed proximally anddistally, the lateral dimension is relative to the width of the jaws 16a, 16 b and is directed laterally (outward) or medially (inward), andthe vertical dimension is relative to the height of the jaws 16 a, 16 band is directed by opening and closing relative to one another.

As best shown in FIG. 6, jaws 16 a, 16 b preferably comprise elongated,substantially rectangular, centrally located tissue support members 58a, 58 b which protrude from base portions 60 a, 60 b towards oneanother. As shown, support members 58 a, 58 b and base portions 60 a, 60b may comprise a unitarily formed single piece. However, in alternativeembodiments, as shown in FIG. 16, support members 58 a, 58 b and baseportions 60 a, 60 b may comprise separately formed connected pieces.

As shown in FIG. 6, support members 58 a, 58 b provide anvils fordirectly opposing tissue grasping surfaces 62 a, 62 b. As shown in FIGS.3 and 4, when the jaws 16 a, 16 b are open the grasping surfaces 62 a,62 b converge proximally and diverge distally.

Grasping surfaces 62 a, 62 b further comprise electrically insulativesurfaces which are preferably provided by support members 58 a, 58 b andbase portions 60 a, 60 b comprising electrically insulating materials.In this manner, support members 58 a, 58 b and base portions 60 a, 60 bmay be electrically insulated relative to electrodes 64 a, 66 a, 64 b,66 b discussed in greater detail below.

In some embodiments, the electrically insulating material may comprisean electrically insulating polymer, either thermoplastic or thermoset,reinforced or unreinforced, filled or unfilled. Exemplary polymermaterials include, but are not limited to, polyacetal (POM), polyanmide(PA), polyamideimide (PAI), polyetheretherketone (PEEK), polyetherimide(PEI), polyethersulfone (PES), polyimide (PI), polyphenylenesulfide(PPS), polyphthalamide (PPA), polysulfone (PSO), polytetrafluoroethylene(PTFE) and syndiotactic polystyrene (SPS). More preferably, theelectrically insulating polymer comprises either a liquid crystalpolymer and, more particularly, an aromatic liquid crystal polyesterwhich is reinforced with glass fiber, such as Vectra® A130 from Ticona,or Ultem® 10% glass filled polyetherimide from the General ElectricCompany. Exemplary reinforcement materials for polymers include, but arenot limited to, glass fibers and boron fibers. Exemplary fillermaterials for polymers include mica, calcium carbonate and boronnitride. Reinforcement materials for the polymer material may bepreferable for increased strength while filler materials may bepreferable for increased heat resistance and/or thermal conductivity.Still other electrically insulating materials for support members 58 a,58 b and base portions 60 a, 60 b may comprise electrically insulatingceramics such as boron nitride.

In order that heat may be transferred away from surfaces 62 a, 62 bduring use of device 10, preferably the material for support members 58a, 58 b and base portions 60 a, 60 b has a thermal conductivity k_(tc)at 300° K (Kelvin) equal or greater than about 0.01 watt/cm° K. Morepreferably, the material for support members 58 a, 58 b and baseportions 60 a, 60 b has a thermal conductivity k_(tc) at 300° K (Kelvin)equal or greater than about 0.16 watt/cm° K. Even more preferably, thematerial for support members 58 a, 58 b and base portions 60 a, 60 b hasa thermal conductivity k_(tc) at 300° K (Kelvin) equal or greater thanabout 0.35 watt/cm° K.

In addition to grasping surfaces 62 a, 62 b comprising electricallyinsulating surfaces, preferably grasping surfaces 62 a, 62 b aresubstantially flat and provide for tissue removal there from.Furthermore, preferably grasping surfaces 62 a, 62 b also comprisehydrophobic surfaces to reduce the presence of fluid (e.g. conductivefluid 128 from fluid source 130; blood and other bodily fluids) on andbetween the grasping surfaces 62 a, 62 b, particularly those portionswhich are unoccupied by tissue during treatment.

However, so that grasping surfaces 62 a, 62 b don't become so smooththat tissue therebetween may slide out, preferably the surfaces 62 a, 62b are not highly polished smooth surfaces. In other words, preferablysurfaces 62 a, 62 b have a surface roughness or asperity of surface inthe range between and including about 20 microns to 500 microns where 10microns is indicative of a polished surface. More preferably, 62 a, 62 bsurfaces have a surface roughness in the range between and includingabout 25 microns to 250 microns. Furthermore, in various embodiments,surfaces 62 a, 62 b may comprise textured surfaces (a surface which isnot smooth, but rather includes a raised pattern on it), such as astipple textured surfaces. Also, in various embodiments, surfaces 62 a,62 b may include serrations 67 (as shown in FIG. 17).

In certain applications, it may be necessary to further increase thethermal conductivity of support members 58 a, 58 b and base portions 60a, 60 b to better function as heat sinks to remove heat transferred tosurfaces 62 a, 62 b from tissue there between. In alternativeembodiments as shown in FIG. 8, jaws 16 a, 16 b comprise an electricallyinsulative, thin (less than about 0.5 mm thick) coating 68 whichprovides grasping surfaces 62 a, 62 b and which overlies support members58 a, 58 b and base portions 60 a, 60 b, which comprise a materialhaving a relatively higher thermal conductivity than the coating 68. Forexample, the insulative coating 68 may comprise a polymer coatingapplied over an underlying metal. In such an instance, it may bedesirable to make the polymer coating 68 as thin as possible to maximizeheat transfer into the underlying structure. An exemplary electricallyinsulative coating 68 may comprise a fluorinated polymer, such aspolytetrafluoroethylene (PTFE). Exemplary metals which may underlie theelectrically insulative coating are preferably non-corrosive, such asstainless steel, aluminum, titanium, silver, gold and platinum.

Preferably the material for support members 58 a, 58 b and base portions60 a, 60 b underlying the coating 68 has a thermal conductivity k_(tc)at 300° K (Kelvin) equal or greater than about 0.1 watt/cm° K. Morepreferably, the material for support members 58 a, 58 b and baseportions 60 a, 60 b underlying the coating 68 has a thermal conductivityk_(tc) at 300° K (Kelvin) equal or greater than about 1 watt/cm° K. Evenmore preferably, the material for support members 58 a, 58 b and baseportions 60 a, 60 b underlying the coating 68 has a thermal conductivityk_(tc) at 300° K (Kelvin) equal or greater than about 2 watt/cm° K.

As shown in FIG. 8, another structure which may be used to remove heatfrom support members 58 a, 58 b and base portions 60 a, 60 b comprisesone or more heat pipes 63 containing a fluid 65 therein and connected toa heat exchanger as known in the art. Heat pipes 63 may be connected toa heat exchanger thermally isolated from the support members 58 a, 58 band base portions 60 a, 60 b for removing heat from support members 58a, 58 b and base portions 60 a, 60 b, or the heat pipe may beconvectively cooled by fluid 128 provided to the jaws 16 a, 16 b.

As best shown in FIGS. 3-4 and 6, jaw 16 a may include two electrodes 64a, 66 a while jaw 16 b may include two directly opposing electrodes 64b, 66 b. Each electrode 64 a, 66 a, 64 b, 66 b is connectable to thegenerator 136 (as shown in FIG. 9), preferably by being electricallycoupled via wire conductors 40, 42 of insulated wires 36, 38 which areultimately electrically coupled to generator 136. Electrodes 64 a, 66 a,64 b, 66 b preferably comprise a non-corrosive metal, such as stainlesssteel, aluminum, titanium, silver, gold or platinum.

As best shown in FIGS. 3 and 4, preferably electrodes 64 a, 66 a, 64 b,66 b are orientated to extend along the length of the jaws 16 a, 16 bfrom the proximal end portions 70 a, 70 b to the distal end portions 72a, 72 b of grasping surfaces 62 a, 62 b, preferably laterally outsidethe confines and borders of grasping surfaces 62 a, 62 b. Each electrode64 a, 66 a, 64 b, 66 b is preferably configured to be substantiallyparallel to and equally spaced from support members 58 a, 58 b andgrasping surfaces 62 a, 62 b along their respective lengths. However, inalternative embodiments, the electrodes 64 a, 66 a, 64 b, 66 b may notbe substantially parallel, for example, to compensate for a varyingwidth of grasping surfaces 62 a, 62 b or tissue thickness.

Preferably electrodes 64 a, 64 b comprise electrical source electrodeswhile electrodes 66 a, 66 b comprise counter electrodes. As shown inFIG. 6, source electrodes 64 a, 64 b are shown with the positiveelectrical sign (+) while counter electrodes 66 a, 66 b are shown withthe negative electrical sign (−). Thus, the source electrodes 64 a, 64 band counter electrodes 66 a, 66 b have different electrical potentials.Also as shown in FIG. 6, each jaw 16 a, 16 b may comprise one electricalsource electrode and one electrical counter electrode, with the twoelectrodes on each of the jaws 16 a, 16 b configured to have the samepolarity with the directly opposing electrodes on the opposite jaw.

Given the above configuration, electrodes 64 a, 66 a, 64 b, 66 b areconfigured such that electrical current flowing in the tissue betweengrasping surfaces 62 a, 62 b will flow across (substantially parallelto) the grasping surfaces 62 a, 62 b. With electrodes 64 a, 66 a, 64 b,66 b in such a configuration, four possible electrical paths are createdbetween: (1) electrodes 64 a and 66 a; (2) electrodes 64 a and 66 b; (3)electrodes 64 b and 66 b; and (4) electrodes 64 b and 66 a.

The creation of certain of these electrical paths is denoted byelectrical field lines 74 in FIG. 7. It should be noted that the contourof electrical field lines 74 is exemplary. Furthermore, particularlyoutside grasping surfaces 62 a, 62 b, it should be noted that theelectrical field lines 74 are exemplary as to where electrical currentis expected to flow, and not necessarily where the greatest currentdensity is expected to reside.

Returning to FIG. 6, it is to be understood that, within the scope ofthe invention, only one pair of electrodes is required for the invention(as shown in FIG. 17). Furthermore, it is to be understood that, withinthe scope of the invention, where only one electrode pair is utilized,the electrodes do not have to be on the same jaw (as shown in FIG. 10).In other words, the electrodes, while still configured outside of andseparated from opposing edges of grasping surfaces 62 a, 62 b, may beconfigured with one electrode on each jaw (e.g. diagonally arranged).Thus, a suitable electrode pair may comprise any pair of electrodesabove (i.e. 64 a and 66 a; 64 a and 66 b; 64 b and 66 b; 64 b and 66 a)which create any one of the four electrical paths identified.

As indicated above, preferably grasping surfaces 62 a, 62 b alsocomprise hydrophobic surfaces to reduce the presence of fluid on andbetween grasping surfaces 62 a, 62 b, particularly portions which areunoccupied by tissue. Reducing the presence of fluid on unoccupiedportions of surfaces 62 a, 62 b is desirable to inhibit, and morepreferably minimize or prevent, the formation of a conductive fluidshunt. In other words, if conductive fluid forms a bridge across thewidth of surfaces 62 a, 62 b, and the bridge connects an electrode pairconfigured to create an electrical path (i.e. 64 a and 66 a; 64 a and 66b; 64 b and 66 b; 64 b and 66 a), an electrical path through theconductive fluid bridge is created parallel to the electrical paththrough tissue. Consequently, a portion of the electrical energyintended to be provided to tissue is diverted through the conductivefluid bridge and bypasses the tissue. This loss of energy can increasethe time required to treat tissue.

Other than surfaces 62 a, 62 b comprising hydrophobic surfaces, in orderto reduce the presence of fluid on and between the unoccupied portionsof grasping surfaces 62 a, 62 b of device 10, preferably the contactangle θ of fluid droplets, particularly of fluid 128, on graspingsurfaces 62 a, 62 b is about 30 degrees or greater after the droplet hasstabilized from initial placement thereon. More preferably, the contactangle θ of fluid droplets, particularly of fluid 128, on graspingsurfaces 62 a, 62 b is about 45 degrees or greater. More preferably, thecontact angle θ of fluid droplets, particularly of fluid 128, ongrasping surfaces 62 a, 62 b is about 60 degrees or greater. Even morepreferably, the contact angle θ of fluid droplets, particularly of fluid128, on grasping surfaces 62 a, 62 b is about 75 degrees or greater.Most preferably, the contact angle θ of fluid droplets, particularly offluid 128, on grasping surfaces 62 a, 62 b is about 90 degrees orgreater.

Contact angle, θ, is a quantitative measure of the wetting of a solid bya liquid. It is defined geometrically as the angle formed by a liquid atthe three phase boundary where a liquid, gas and solid intersect. Interms of the thermodynamics of the materials involved, contact angle θinvolves the interfacial free energies between the three phases given bythe equation γ_(LV) cos θ=γ_(SV)−γ_(SL) where γ_(LV), γ_(SV) and γ_(SL)refer to the interfacial energies of the liquid/vapor, solid/vapor andsolid/liquid interfaces, respectively. If the contact angle θ is lessthan 90 degrees the liquid is said to wet the solid. If the contactangle is greater than 90 degrees the liquid is non-wetting. A zerocontact angle θ represents complete wetting.

For clarification, while it is known that the contact angle θ may bedefined by the preceding equation, in reality contact angle θ isdetermined by a various models to an approximation. According topublication entitled “Surface Energy Calculations” (dated Sep. 13, 2001)from First Ten Angstroms (465 Dinwiddie Street, Portsmouth, Va. 23704),there are five models which are widely used to approximate contact angleθ and a number of others which have small followings. The fivepredominate models and their synonyms are: (1) Zisman critical wettingtension; (2) Girifalco, Good, Fowkes, Young combining rule; (3) Owens,Wendt geometric mean; (4) Wu harmonic mean; and (5) Lewis acid/basetheory. Also according to the First Ten Angstroms publication, forwell-known, well characterized surfaces, there can be a 25% differencein the answers provided for the contact angle θ by the models. Any oneof the five predominate models above which calculates a contact angle θrecited by a particular embodiment of the invention should be consideredas fulfilling the requirements of the embodiment, even if the remainingfour models calculate a contact angle θ which does not fulfill therecitation of the embodiment.

As best shown in FIGS. 3-4 and 6, in certain embodiments, each electrode64 a, 66 a, 64 b, 66 b comprises an elongated structure extendinglongitudinally on jaws 16 a, 16 b. As best shown in FIG. 6, electrodes64 a, 66 a, 64 b, 66 b preferably each comprise generally tubularstructures having cylindrical outer surfaces 76 a, 78 a, 76 b, 78 b withsubstantially uniform diameters. Preferably, electrodes 64 a, 66 a, 64b, 66 b have a cross-sectional dimension (e.g. diameter) in the rangebetween and including about 0.1 mm to 4 mm and more preferably have adiameter in the range between and including about 1 mm to 2 mm.

As shown in FIGS. 3 and 4, in certain embodiments, electrodes 64 a, 66a, 64 b, 66 b have distal end wall portions 80 a, 82 a, 80 b, 82 bcomprising generally domed shapes. In this manner, the distal ends ofelectrodes 64 a, 66 a, 64 b, 66 b preferably provide smooth, bluntcontour outer surfaces which are devoid of sharp edges.

It should be understood that the structure providing electrodes 64 a, 66a, 64 b, 66 b need not wholly-comprise an electrically conductivematerial. In other words, for example, only the tissueinteracting/treating surfaces 76 a, 78 a, 76 b, 78 b of electrodes 64 a,66 a, 64 b, 66 b need be electrically conductive. Thus, for example, theexemplary tubular structure for electrodes 64 a, 66 a, 64 b, 66 b maycomprise an electrically conductive coating, such as metal, overlying anelectrically insulative material, such as a polymer or ceramic.

As best shown by FIG. 5, the surfaces 76 a, 78 a, 76 b, 78 b ofelectrodes 64 a, 66 a, 64 b, 66 b for treating tissue preferablyterminate proximal to the distal end of a cutting mechanism 32 (where acutting mechanism is employed), which preferably comprises a planarblade with a sharpened distal end. Cutting mechanism 32 is extendablefrom the distal end 18 of shaft 12 and travels on and along a centerplane CP that is perpendicular to grasping surfaces 62 a, 62 b (as shownin FIG. 6) and segments the jaws 16 a, 16 b into opposing first andsecond sides (i.e. left-side portion and right-side portion), which aresymmetrical in certain embodiments. Cutting mechanism 32 travels bothlongitudinally proximally and distally in an elongated travel slot 33 a,33 b. Cutting mechanism 32 is particularly used with endoscopic versionsof device 10. In this manner, device 10 is configured to treat tissueproximal to the distal end of the cutting mechanism 32 which reduces thepossibility of cutting untreated or partially treated tissue withcutting mechanism 32 when activated.

In contrast to the contact angle θ of fluid droplets on device graspingsurfaces 62 a, 62 b most preferably being about 90 degrees or greater,preferably the contact angle θ of fluid droplets, particularly fluid128, on surfaces 76 a, 78 a, 76 b, 78 b of electrodes 64 a, 66 a, 64 b,66 b is about 90 degrees or less after the droplet has stabilized frominitial placement thereon. More preferably, the contact angle θ of fluiddroplets, particularly fluid 128, on surfaces 76 a, 78 a, 76 b, 78 b ofelectrodes 64 a, 66 a, 64 b, 66 b is about 75 degrees or less. Morepreferably, the contact angle θ of fluid droplets, particularly fluid128, on surfaces 76 a, 78 a, 76 b, 78 b of electrodes 64 a, 66 a, 64 b,66 b is about 60 degrees or less. Even more preferably, the contactangle θ of fluid droplets, particularly fluid 128, on surfaces 76 a, 78a, 76 b, 78 b of electrodes 64 a, 66 a, 64 b, 66 b is about 45 degreesor less. Most preferably, the contact angle θ of fluid droplets,particularly fluid 128, on surfaces 76 a, 78 a, 76 b, 78 b of electrodes64 a, 66 a, 64 b, 66 b is about 30 degrees or less.

Preferably fluid 128 (shown in FIGS. 7 and 9) wets the surfaces 76 a, 78a, 76 b, 78 b of electrodes 64 a, 66 a, 64 b, 66 b such that the fluid128 forms a thin, continuous film coating at least partially thereon anddoes not form isolated rivulets or circular beads which freely run offthe surfaces 76 a, 78 a, 76 b, 78 b of electrodes 64 a, 66 a, 64 b, 66b.

As shown in FIG. 7, each jaw 16 a, 16 b preferably comprises at leastone fluid flow passage and outlet configured to provide fluid 128 tosurfaces 166 a, 166 b of tissue 156 and/or surfaces 76 a, 78 a, 76 b, 78b of electrodes 64 a, 66 a, 64 b, 66 b, and/or therebetween. To minimizecomplexity, preferably a portion of an electrode forms at least aportion of the fluid flow passage.

As best shown in FIGS. 3-4 and 6, in certain embodiments, each electrode64 a, 66 a, 64 b, 66 b is hollow and comprises a rectilinear,longitudinally extending, cavity forming a central (primary) fluid flowpassage 84 a, 86 a, 84 b, 86 b for fluid 128. To minimize complexity,each electrode 64 a, 66 a, 64 b, 66 b may be formed from hypodermictubing and the central flow passages 84 a, 86 a, 84 b, 86 b comprise thelumens of the hypodermic tubing. Furthermore, as shown in FIG. 6, thehypodermic tubing provides a cornerless electrode to distributeelectrical energy to the tissue more uniformly and avoid concentratededge effects typically encountered with the transmission of electricalenergy through electrodes having sharp edges.

As best shown in FIGS. 3-4 and 5, each central flow passage 84 a, 86 a,84 b, 86 b is preferably orientated to extend along the length of thejaws 16 a, 16 b from the proximal end portions 70 a, 70 b to the distalend portions 72 a, 72 b of grasping surfaces 62 a, 62 b of the jaws 16a, 16 b, preferably laterally outside grasping surfaces 62 a, 62 b.Also, as shown, each central flow passage 84 a, 86 a, 84 b, 86 b ispreferably configured to extend along the length of the jaws 16 a, 16 bcoextensively with electrodes 64 a, 66 a, 64 b, 66 b. Furthermore, asshown, each central flow passage 84 a, 86 a, 84 b, 86 b is preferablyconfigured to be substantially parallel to and equally spaced fromsupport members 58 a, 58 b and grasping surfaces 62 a, 62 b along theirrespective lengths.

As shown in FIGS. 3 and 4, preferably each central flow passage 84 a, 86a, 84 b, 86 b has a central flow passage fluid entrance opening 88 a, 90a, 88 b, 90 b located near the proximal end 54 of jaws 16 a, 16 b. Alsoas shown, each central flow passage 84 a, 86 a, 84 b, 86 b isconnectable to the fluid source 130 (shown in FIG. 9), preferably bybeing fluidly coupled with the passage 46 of flexible tube 44 which isultimately fluidly coupled to fluid source 130.

In addition to central flow passages 84 a, 86 a, 84 b, 86 b, as bestshown in FIG. 6, the flow passages also preferably comprise at least onerectilinear, radially directed, side (secondary) fluid flow passage 92a, 94 a, 92 b, 94 b which is fluidly coupled to each central flowpassage 84 a, 86 a, 84 b, 86 b. More preferably, as shown in FIGS. 3-6,each fluid flow passage preferably comprises a plurality of side flowpassages 92 a, 94 a, 92 b, 94 b which are defined and spaced preferablyboth longitudinally and circumferentially around electrodes 64 a, 66 a,64 b, 66 b and central flow passages 84 a, 86 a, 84 b, 86 b. Alsopreferably, as shown the side flow passages 92 a, 94 a, 92 b, 94 b aredefined and spaced from the proximal end portions 70 a, 70 b to thedistal end portions 72 a, 72 b of grasping surfaces 62 a, 62 b of eachjaw 16 a, 16 b.

Also as shown, side flow passages 92 a, 94 a, 92 b, 94 b preferably eachhave a cross-sectional dimension, more specifically diameter, andcorresponding cross-sectional area, less than the portion of centralflow passage 84 a, 86 a, 84 b, 86 b from which fluid 128 is provided.Also as shown, the side flow passages 92 a, 94 a, 92 b, 94 b extendthrough the cylindrical portion of the electrodes 64 a, 66 a, 64 b, 66 band are preferably formed substantially at a right angle (e.g. withinabout 10 degrees of a right angle) to the central flow passages 84 a, 86a, 84 b, 86 b both longitudinally and circumferentially. Also as shown,the side flow passages 92 a, 94 a, 92 b, 94 b are preferably formedsubstantially at a right angle to the tissue interacting/treatingcylindrical surfaces 76 a, 78 a, 76 b, 78 b of electrodes 64 a, 66 a, 64b, 66 b.

Preferably, side flow passages 92 a, 94 a, 92 b, 94 b extend fromcentral flow passages 84 a, 86 a, 84 b, 86 b to side flow passage fluidexit openings 96 a, 98 a, 96 b, 98 b located on surfaces 76 a, 78 a, 76b, 78 b. More preferably, side flow passages 92 a, 94 a, 92 b, 94 b andassociated side flow passage fluid exit openings 96 a, 98 a, 96 b, 98 bare defined and spaced both longitudinally and circumferentially aroundthe surfaces 76 a, 78 a, 76 b, 78 b, along the length of the jaws 16 a,16 b from the proximal end portions 70 a, 70 b to the distal endportions 72 a, 72 b of grasping surfaces 62 a, 62 b of the jaws 16 a, 16b.

As shown in FIGS. 3-6, preferably the plurality of side flow passages 92a, 94 a, 92 b, 94 b, and corresponding side flow passage fluid exitopenings 96 a, 98 a, 96 b, 98 b are configured to form both longitudinaland circumferential straight rows, and are preferably uniformly spacedrelative to one another. Also preferably, the plurality of side flowpassages 92 a, 94 a, 92 b, 94 b are configured to distribute fluid flowexiting from side flow passage fluid exit openings 96 a, 98 a, 96 b, 98b substantially uniformly.

Preferably, side flow passages 92 a, 94 a, 92 b, 94 b have across-sectional dimension (e.g. diameter) in the range between andincluding about 0.1 mm to 1 mm and more preferably have a diameter inthe range between and including about 0.15 mm to 0.2 mm. As for centralflow passages 84 a, 86 a, 84 b, 86 b, preferably central fluid flowpassages 84 a, 86 a, 84 b, 86 b have a cross-sectional dimension (e.g.diameter) in the range between and including about 0.2 mm to 2 mm andmore preferably have a diameter in the range between and including about0.5 mm to 1 mm.

As shown FIGS. 3 and 4, distal wall portions 80 a, 82 a, 80 b, 82 b atleast partially provide and define the distal ends of central flowpassages 84 a, 86 a, 84 b, 86 b, respectively. Also as shown, preferablywall portions 80 a, 82 a, 80 b, 82 b completely provide and define thedistal ends of central flow passages 84 a, 86 a, 84 b, 86 b such thatthe distal ends of the central fluid flow passages 84 a, 86 a, 84 b, 86b preferably comprise blind ends. Consequently, the central flowpassages 84 a, 86 a, 84 b, 86 b preferably do not continue completelythrough electrodes 64 a, 66 a, 64 b, 66 b. Rather, the distal ends ofthe central flow passages 84 a, 86 a, 84 b, 86 b terminate within theconfines of the electrodes 64 a, 66 a, 64 b, 66 b and are closed by astructure, here wall portions 80 a, 82 a, 80 b, 82 b forming the distalends of central flow passages 84 a, 86 a, 84 b, 86 b.

However, wall portions 80 a, 82 a, 80 b, 82 b need not completelyocclude and define the distal ends of central flow passages 84 a, 86 a,84 b, 86 b. In other words, rather than extending only partially throughelectrodes 64 a, 66 a, 64 b, 66 b, central flow passages 84 a, 86 a, 84b, 86 b may extend completely through electrodes 64 a, 66 a, 64 b, 66 band have a distal end opening. However, in such an instance, a wallportions 80 a, 82 a, 80 b, 82 b should substantially occlude and inhibitfluid 128 from exiting from the central flow passage distal end exitopening. With regards to this specification, occlusion of a central flowpassage distal end exit opening and the corresponding inhibiting of flowfrom exiting from the central flow passage distal end exit openingshould be considered substantial when the occlusion and correspondinginhibiting of flow results in increased flow from the side flow passagefluid exit openings 96 a, 98 a, 96 b, 98 b of side flow passages 92 a,94 a, 92 b, 94 b. In other words, wall portions 80 a, 82 a, 80 b, 82 bmerely need to function as fluid flow diverters and redirect a portionof the fluid 128 coming in contact therewith from flowing parallel withthe longitudinal axis of the central fluid flow passages 84 a, 86 a, 84b, 86 b to flowing radially from the longitudinal axis through side flowpassages 92 a, 94 a, 92 b, 94 b.

As shown, wall portions 80 a, 82 a, 80 b, 82 b are preferably integral,and more preferably unitary, with the remainder of electrodes 64 a, 66a, 64 b, 66 b. Where electrodes 64 a, 66 a, 64 b, 66 b are provided byhypodermic tubing, closure or occlusion of the central flow passages 84a, 86 a, 84 b, 86 b may be accomplished by welding or crimping (as bestshown in FIGS. 20 and 21) a previously open distal end of the hypodermictubing. In alternative embodiments, wall portions 80 a, 82 a, 80 b, 82 bmay be provided by a separate plug inserted into the distal end portionof central flow passages 84 a, 86 a, 84 b, 86 b. Also in alternativeembodiments, wall portions 80 a, 82 a, 80 b, 82 b may be provided bydistal end portions 100 a, 100 b of jaws 16 a, 16 b.

Jaws 16 a, 16 b preferably comprise at least one connector portion forattaching electrodes 64 a, 66 a, 64 b, 66 b thereto. As shown in FIGS. 3and 4, the connector portions preferably comprise receptacles 102 a, 104a, 102 b, 104 b connected laterally adjacent to the support members 58a, 58 b and located at the distal end portions 100 a, 100 b of jaws 16a, 16 b. As shown in FIGS. 3 and 4, the connector portions for attachingelectrodes 64 a, 66 a, 64 b, 66 b to jaws 16 a, 16 b are verticallyadjacent base portions 60 a, 60 b and protrude from base portions 60 a,60 b towards one another in the same manner as support members 58 a, 58b.

Preferably, receptacles 102 a, 104 a, 102 b, 104 b are formed unitarilywith support members 58 a, 58 b as single pieces and provide a housingcomprising cylindrical blind holes for containing distal end cylindricalportions 106 a, 108 a, 106 b, 108 b of electrodes 64 a, 66 a, 64 b, 66b. The distal end cylindrical portions 106 a, 108 a, 106 b, 108 b of theelectrodes 64 a, 66 a, 64 b, 66 b located in the receptacles 102 a, 104a, 102 b, 104 b preferably form an interference fit within thereceptacles 102 a, 104 a, 102 b, 104 b to inhibit removal therefrom.

Preferably jaws 16 a, 16 b also comprise a second connector portion forattaching electrodes 64 a, 66 a, 64 b, 66 b thereto. As shown in FIGS. 3and 4, the connector portions preferably comprise receptacles 110 a, 112a, 110 b, 112 b connected laterally adjacent to the support members 58a, 58 b and located at the proximal end portions 114 a, 114 b of jaws 16a, 16 b.

Preferably, receptacles 110 a, 112 a, 110 b, 112 b are also formedunitarily with support members 58 a, 58 b as single pieces and provide ahousing comprising cylindrical through holes for containing proximal endcylindrical portions 116 a, 118 a, 116 b, 118 b of electrodes 64 a, 66a, 64 b, 66 b. The proximal end cylindrical portions 116 a, 118 a, 116b, 118 b of the electrodes 64 a, 66 a, 64 b, 66 b located in thereceptacles 110 a, 112 a, 110 b, 112 b preferably form an interferencefit within the receptacles 110 a, 112 a, 110 b, 112 b to inhibit removaltherefrom.

In certain situations tissue laterally outside grasping surfaces 62 a,62 b may be compressed by a portion of the jaws 16 a, 16 b, particularlyelectrodes 64 a, 66 a, 64 b, 66 b. In order to concentrate a greatmajority of the electrical power converted to heat in the tissue locatedin the medial portion of grasping surfaces 62 a, 62 b (equal to aboutthe middle one-third of the width) preferably the tissue outsidegrasping surfaces 62 a, 62 b will be compressed to a lesser extent (e.g.percentage) than the tissue between grasping surfaces 62 a, 62 b.Consequently, as shown in FIG. 6, preferably surfaces 76 a, 78 a, 76 b,78 b of electrodes 64 a, 66 a, 64 b, 66 b are vertically recessed and,more particularly, stepped down relative to surfaces 62 a, 62 b suchthat the minimum separation distance S_(e) between directly opposingelectrode surfaces 76 a, 76 b and 78 a, 78 b is greater than the minimumseparation distance S_(s) between grasping surfaces 62 a, 62 b. As aresult, tissue which may be partially compressed between surfaces 76 a,76 b and 78 a, 78 b, for example, will be heated less than tissue in themedial portion of surfaces 62 a, 62 b which is more fully compressed.However, as shown in FIG. 7, surfaces 76 a, 78 a, 76 b, 78 b should notbe stepped down relative to surfaces 62 a, 62 b such that electricalcoupling is not maintained with surfaces 166 a, 166 b of tissue 156 andfluid couplings 160 and 162 (discussed in greater detail below) areunable to couple the surfaces 76 a, 78 a, 76 b, 78 b with surfaces 166a, 166 b of tissue 156.

Continuing with FIG. 6, surfaces 76 a, 78 a, 76 b, 78 b of electrodes 64a, 66 a, 64 b, 66 b are preferably configured such that the portion ofsurfaces 76 a, 78 a, 76 b, 78 b closest to grasping surfaces 62 a, 62 bis remotely located and spatially separated from grasping surfaces 62 a,62 b. More specifically, as shown, the portion of surfaces 76 a, 78 a,76 b, 78 b closest grasping surfaces 62 a, 62 b is remotely separatedboth laterally and vertically from grasping surfaces 62 a, 62 b.Furthermore, as shown, preferably the portion of surfaces 76 a, 78 a, 76b, 78 b closest to grasping surfaces 62 a, 62 b is remotely separatedfrom grasping surfaces 62 a, 62 b by air gaps 119 (which are ultimatelyoccupied by fluid couplings 160 discussed below).

As shown in FIG. 6, the air gaps 119 are defined by two sides relativeto device 10. More specifically, the air gaps 119 are defined by aportion of the surface of lateral side surfaces 121 a, 121 b of supportmembers 58 a, 58 b and a portion of the surfaces 76 a, 78 a, 76 b, 78 bof electrodes 64 a, 66 a, 64 b, 66 b. Air gaps 119 preferably have awidth (e.g. shortest distance between an electrode surface and an edgeof a tissue grasping surface) greater than about 0.5 mm, and in therange between and including about 0.5 mm to 5.0 mm. More preferably, airgaps 119 preferably have a width greater than about 1 mm, in the rangebetween and including about 1 mm to 3.0 mm.

In the presence of tissue 156 as shown in FIG. 7, the air gaps 119 maybe further defined by a portion of the surfaces 166 a, 166 b of tissue156. As shown, the portion of the surfaces 166 a, 166 b of tissue 156preferably extends between a separation point 123 from electrodes 64 a,66 a, 64 b, 66 b and edges 125 a, 125 b to grasping surfaces 29 a, 29 b.Among other things, these three sides help to shape fluid couplings 160into the triangular shape described below.

Given that air gaps 119 are elongated in that they extend longitudinallyalong the length of surfaces 62 a, 62 b and electrodes 64 a, 66 a, 64 b,66 b, the air gaps 119 also provide an open fluid flow channel or troughfor fluid 128 from fluid source 130 to flow along the length of surfaces62 a, 62 b and electrode surfaces 76 a, 78 a, 76 b, 78 b.

As shown in FIG. 6, the outer perimeter edges 125 a, 125 b to graspingsurfaces 62 a, 62 b of jaws 16 a, 16 b comprise sharp edges. However, inother embodiments, as shown in FIG. 8, edges 125 a, 125 b may comprisebevel edges. Edges 125 a, 125 b preferably comprise beveled edges ratherthan sharp edges to inhibit inadvertent cutting of tissue 156. However,more importantly, beveled edges are configured to further concentrate agreat majority of the electrical power converted to heat in the tissuelocated in the medial portion of grasping surfaces 62 a, 62 b. In stillother embodiments, as shown in FIG. 16, edges 125 a, 125 b may comprisea polymer, such as provided by a coating 127, for example, of PTFE whilegrasping surfaces 62 a, 62 b comprise a ceramic such as boron nitride.

As shown in FIGS. 3-6 distal end portions 100 a, 100 b of jaws 16 a, 16b preferably comprise a generally domed shape, and provide anobstruction (e.g. the structure forming receptacles 102 a, 104 a, 102 b,104 b for inhibiting fluid 128 from flowing around the distal end 56 ofthe jaws 16 a, 16 b and forming a conductive fluid bridge which may forma shunt between certain electrode pairs having different polarities(e.g. 64 a, 66 a and 64 b, 66 b).

Similarly to distal end portions 100 a, 100 b, proximal end portions 114a, 114 b of jaws 16 a, 16 b also provide an obstruction (e.g. thestructure forming receptacles 110 a, 112 a, 110 b, 112 b) for inhibitingfluid 128 from flowing around the proximal end 54 of the jaws 16 a, 16 band forming a conductive fluid bridge which may form a shunt betweencertain electrode pairs having different polarities (e.g. 64 a, 66 a and64 b, 66 b).

As shown in FIG. 6, base portions 60 a, 60 b preferably comprise amaximum lateral (width) dimension d equal to or less than the maximumlateral dimension of electrodes 64 a, 66 a, 64 b, 66 b. In this manner,the electrical coupling of tissue to electrodes 64 a, 66 a, 64 b, 66 bis less likely to be disrupted if tissue contacts base portions 60 a, 60b during use of device 10.

Continuing with FIG. 6, preferably the contour of backside surfaces 120a, 120 b of jaws 16 a, 16 b provides one or more obstructions whichinhibits fluid 128 from flowing around the backside of the jaws 16 a, 16b and forming a conductive fluid bridge which may form a shunt betweencertain electrode pairs having different polarities (e.g. 64 a, 66 a and64 b, 66 b). As shown, the contour of the backside surfaces 120 a, 120 bpreferably comprises one or more longitudinally extending protrusions122 a, 122 b which provide drip edges 124 a, 124 b for fluid 128 toseparate from device 10. If a protrusion 122 a, 122 b is not utilized(possibly due to size constraints), the contour of the backside surfaces120 a, 120 b may comprise one or more longitudinally extending recesses126 a, 126 b which also provides drip edges 124 a, 124 b adjacentthereto for fluid 128 to separate from device 10. In the above manner,conductive fluid 128 flowing medially around the backside of the jaws 16a, 16 b is inhibited from forming a bridge across the backside surfaces120 a, 120 b of the jaws 16 a, 16 b and may be redirected to flow alongthe length of the jaws 16 a, 16 b, either proximally or distally, untilseparation therefrom.

As indicated above, device 10 may be used as part of a system. FIG. 9shows a block diagram of one exemplary embodiment of a system of theinvention. As shown in FIG. 9, fluid 128 is provided from a fluid source130 through a fluid source output fluid line 132 which is acted on by apump 134 that is connected to input fluid line 44 to electrosurgicaldevice 10.

In a preferred embodiment, the output fluid line 132 and the input fluidline 44 are flexible and are made from a polymer material, such aspolyvinylchloride (PVC) or polyolefin (e.g. polypropylene,polyethylene). In another embodiment, the output fluid line 132 and theinput fluid line 44 are preferably connected via a male and femalemechanical fastener configuration 133, preferably comprising a Luer-Lok®connection from Becton, Dickinson and Company.

Preferably, fluid 128 comprises a saline solution and, more preferablysterile, physiologic saline. It should be understood that wheredescription herein references the use of saline as the fluid 128, otherelectrically conductive fluids, as well as non-fluids, can be used inaccordance with the invention.

For example, in addition to the conductive fluid comprising physiologicsaline (also known as “normal” saline, isotonic saline or 0.9weight-volume percentage sodium chloride (NaCl) solution), theconductive fluid may comprise hypertonic saline solution, hypotonicsaline solution, Ringers solution (a physiologic solution of distilledwater containing specified amounts of sodium chloride, calcium chloride,and potassium chloride), lactated Ringer's solution (a crystalloidelectrolyte sterile solution of distilled water containing specifiedamounts of calcium chloride, potassium chloride, sodium chloride, andsodium lactate), Locke-Ringer's solution (a buffered isotonic solutionof distilled water containing specified amounts of sodium chloride,potassium chloride, calcium chloride, sodium bicarbonate, magnesiumchloride, and dextrose), or any other electrolyte solution. In otherwords, a solution that conducts electricity via an electrolyte, asubstance (salt, acid or base) that dissociates into electricallycharged ions when dissolved in a solvent, such as water, resultingsolution comprising an ionic conductor.

In certain embodiments as discussed herein, hypertonic saline, saturatedwith NaCl to a concentration of about 15% (weight-volume percentage),may be preferred to physiologic saline to reduce the electricalresistivity of the saline from about 50 ohm-cm at 0.9% to about 5 ohm-cmat 15% This ten-fold reduction in electrical resistivity of theconductive fluid will enhance the reduction in heating (both resistanceheating and conduction heating) of tissue and the conductive fluiditself as shown herein.

While a conductive fluid is preferred, as will become more apparent withfurther reading of this specification, the fluid 128 may also comprisean electrically non-conductive fluid. The use of a non-conductive fluidis less preferred to that of a conductive fluid as the non-conductivefluid does not conduct electricity. However, the use of a non-conductivefluid still provides certain advantages over the use of a dry electrodeincluding, for example, thermal cooling and reduced occurrence of tissuesticking to the electrodes of the device 10. Therefore, it is alsowithin the scope of the invention to include the use of a non-conductingfluid, such as, for example, deionized water or 1.5% glycine.

Returning to FIG. 9, energy to heat tissue is provided from an energysource, such as an electrical generator 136 which may providealternating current, RF electrical energy at various rates (i.e. power)to electrodes 64 a, 66 a, 64 b, 66 b. As to the frequency of the RFelectrical energy, it is preferably provided within a frequency band(i.e. a continuous range of frequencies extending between two limitingfrequencies) in the range between and including about 9 kHz (kilohertz)to 300 GHz (gigahertz). More preferably, the RF energy is providedwithin a frequency band in the range between and including about 50 kHz(kilohertz) to 50 MHz (megahertz). Even more preferably, the RF energyis provided within a frequency band in the range between and includingabout 200 kHz (kilohertz) to 2 MHz (megahertz). Most preferably, RFenergy is provided within a frequency band in the range between andincluding about 400 kHz (kilohertz) to 600 kHz (kilohertz).

As shown, the system may be configured to first direct the RF power fromthe generator 136 via a cable 138 to a power measurement device 140 thatmeasures the actual RF power provided from the generator 136. In oneexemplary embodiment, preferably the power measurement device 140 doesnot turn the RF power off or on, or alter the RF power in any way.Rather, a power switch 142 connected to the generator 136 is preferablyprovided by the generator manufacturer and is used to turn the generator136 on and off.

The power switch 142 can comprise any switch to turn the power on andoff, and is commonly provided in the form of a footswitch or othereasily operated switch, such as a switch 142 a mounted on theelectrosurgical device 10. The power switch 142 or 142 a may alsofunction as a manually activated device for increasing or decreasing therate of energy provided from the surgical device 10. Alternatively,internal circuitry and other components of the generator 136 may be usedfor automatically increasing or decreasing the rate of energy providedto the surgical device 10. The particular form of switch 142 a is notimportant to device 10 and any time of suitable switch known in the artmay be used.

As shown in FIG. 9, in series after power measurement device 140, cable34 of device 10 is connected to power measurement device 140 to providethe RF power from generator 136 to the device 10. Alternatively, inother embodiments, power measurement device 140 may be eliminated andcable 34 may be connected directly to generator 136.

Power P is preferably measured before it reaches the electrosurgicaldevice 10. For the situation where capacitive and inductive effects arenegligibly small, from Ohm's law, power P, or the rate of energydelivery (e.g. joules/sec), may be expressed by the product of currenttimes voltage (i.e. I×V), the current squared times resistance (i.e.I²×R), or the voltage squared divided by the resistance (i.e. V²/R);where the current I may be measured in amperes, the voltage V may bemeasured in volts, the electrical resistance R may be measured in ohms,and the power P may be measured in watts (joules/sec). Given that powerP is a function of current I, voltage V, and resistance (impedance) R asindicated above, it should be understood, that a change in power P isreflective of a change in at least one of the input variables. Thus, onemay alternatively measure changes in such input variables themselves,rather than power P directly, with such changes in the input variablesmathematically corresponding to a changes in power P as indicated above.Furthermore, it should be understood that the terms “impedance” and“resistance” as used herein are used interchangeably given thecapacitive and inductive effects are considered negligible.

Heating of the tissue is preferably performed by means of electricalresistance heating. In other words, increasing the temperature of thetissue as a result of electric current flow through the tissue, with theassociated electrical energy being converted into thermal energy (i.e.heat) via accelerated movement of ions as a function of the tissue'selectrical resistance. Resistance heating provides direct, instantaneousheating inside tissue due to the current flow through the tissue.

Heating of the tissue is also accomplished by thermal conductionheating. With conduction, tissue is heated by thermal energy flowingthrough tissue to adjacent tissue by virtue of gradients in temperature.The source of the conduction heating is ultimately from the resistanceheating.

Once a steady-state condition has been achieved, and all temperatureseverywhere in the vicinity of the electrodes and grasped tissue are notchanging with time, it is a reasonable approximation to assume that allheat delivered to tissue by RF power is ultimately carried away by theconvective cooling of the flowing fluid 128. Thus, the flow of the fluid128 not only physically surrounds the grasped tissue, but it also can beseen as a cooling blanket around the targeted tissue treatment site andalso limits the maximum temperature of the fluid 128 heated by tissue byforcing the heated fluid to drip off the electrodes and jaws of thedevice as the fluid 128 is replenished.

In one exemplary embodiment, the system may comprise a flow ratecontroller 144. Preferably, the flow rate controller 144 is configuredto actively link and mathematically relate the power P and the flow rateQ of fluid 128 to one another. Preferably, the controller 144 receivesan input related to the level of RF power being provided from thegenerator 136 (e.g. from power measurement device 140), and adjusts theflow rate Q of the fluid 128 to device 10, thereby adjusting thetemperature (preferably within a predetermined range) of tissue,particularly outside the targeted tissue treatment site (i.e. outsidesurfaces 62 a, 62 b).

In one embodiment, the flow rate controller 144 may receive an inputsignal 146 (e.g. from the power measurement device 140) and calculate anappropriate mathematically predetermined fluid flow rate Q to achieve apredetermined tissue and/or fluid temperature. The flow rate controllermay include a selection switch 148 that can be set to provide a safetyfactor (e.g. 10%, 20%, 30%) beyond the mathematically predeterminedfluid flow rate Q. An output signal 150 from the flow rate controller144 may then be sent to the pump 134 which is correlated to thepredetermined flow rate Q of fluid 128, and thereby provide anappropriate fluid flow rate Q which corresponds to the power P beingprovided by the generator 136.

In another exemplary embodiment, elements of the system are physicallyincluded together in one electronic enclosure. One such embodiment isshown by enclosure within the outline box 152 of FIG. 9. In theillustrated embodiment, the pump 134, flow rate controller 144, andpower measurement device 140 are enclosed within an enclosure, and theseelements are connected through electrical connections to allow signal146 to pass from the power measurement device 140 to the flow ratecontroller 144, and signal 150 to pass from the flow rate controller 144to the pump 134. Other elements of a system can also be included withinone enclosure, depending upon such factors as the desired application ofthe system, and the requirements of the user.

In various embodiments, the flow rate controller 144 of FIG. 9 can be asimple “hard-wired” analog or digital device that requires noprogramming by the user or the manufacturer. The flow rate controller144 can alternatively include a processor, with or without a storagemedium, in which the flow rate Q of fluid 128 is performed by software,hardware, or a combination thereof. In another embodiment, the flow ratecontroller 144 can include semi-programmable hardware configured, forexample, using a hardware descriptive language, such as Verilog. Inanother embodiment, the flow rate controller 144 of FIG. 9 is acomputer, microprocessor-driven controller with software embedded.

In yet another embodiment, the flow rate controller 144 can includeadditional features, such as a delay mechanism, such as a timer, toautomatically keep the flow of fluid 128 on for several seconds afterthe RF power is turned off to provide a post-coagulation cooling of thetissue or “quench,” which can increase the strength of the tissue seal.Also, in another embodiment, the flow rate controller 144 can include adelay mechanism, such as a timer, to automatically turn on the flow offluid 128 several seconds before the RF power is turned on to inhibitthe possibility of undesirable effects as sticking, desiccation, smokeproduction and char formation.

In still another embodiment, the flow rate controller 144 can be used toturn the flow on and off in response to an electrical switch, such as142 a, located in the handle 22. This would automatically turn the flowon when the jaws were clamped on tissue, and turn the flow off when thejaws were unclamped from tissue. As the lever 24 is moved toward thegrip 26 of the handle 22, a normally-closed single pole, single-throwelectrical switch (e.g. switch 142 a) could be activated, completing acircuit, either through the power measurement device 140 or anadditional pair of wires that would exit the handle 22 of device 10 andcontinue directly to the controller 144. Such a switch would function ina manner similar to that of the generator footswitch to turn the RFpower on and off.

Instead of using an electrical switch as described above, a separateon-off flow switch 143 could be located in the handle 22 such that itwould be normally closed when the device jaws were open, and little orno fluid 128 could flow from, for example a fluid source such as apassive gravity-fed saline delivery system. As lever 24 is moved into alatched or use position, clamping the jaws on tissue in a use position,a simple mechanism (push-rod, cam, lever) would open the flow switch 143and allow fluid 128 to flow. This would be one of the simplest forms offlow control, and would be useful to minimize wasteful dripping of fluid128 when the device 10 is not being used, as well as to minimize theamount of fluid 128 that would have to be suctioned out of the patientat a later time.

Also in another embodiment, the flow rate controller 144 can include alow level flow standby mechanism, such as a valve, which continues theflow of fluid 128 at a standby flow level (which prevents the flow ratefrom going to zero when the RF power is turned off) below the surgicalflow level ordinarily encountered during use of device 10.

The pump 134 can be any suitable pump used in surgical procedures toprovide saline or other fluid 128 at a desired flow rate Q. Preferably,the pump 134 comprises a peristaltic pump. With a rotary peristalticpump, typically fluid 128 is conveyed within the confines of fluid line132 by waves of contraction placed externally on the line which areproduced mechanically, typically by rotating rollers which squeezeflexible tubing against a support intermittently. Alternatively, with alinear peristaltic pump, typically a fluid 128 is conveyed within theconfines of a flexible tube by waves of contraction placed externally onthe tube which are produced mechanically, typically by a series ofcompression fingers or pads which squeeze the flexible tubing against asupport sequentially. Peristaltic pumps are generally preferred for useas the electromechanical force mechanism (e.g. rollers driven byelectric motor) does not make contact the fluid 128, thus reducing thelikelihood of inadvertent contamination.

Alternatively, pump 134 can be a “syringe pump”, with a built-in fluidsupply. With such a pump, typically a filled syringe is located on anelectro-mechanical force mechanism (e.g. ram driven by electric motor)which acts on the plunger of the syringe to force delivery of the fluid128 contained therein. Alternatively, the syringe pump may comprise adouble-acting syringe pump with two syringes such that they can drawsaline from a reservoir (e.g. of fluid source 130), eithersimultaneously or intermittently. With a double acting syringe pump, thepumping mechanism is generally capable of both infusion and withdrawal.Typically, while fluid 128 is being expelled from one syringe, the othersyringe is receiving fluid 128 therein from a separate reservoir. Inthis manner, the delivery of fluid 128 remains continuous anduninterrupted as the syringes function in series. Alternatively, itshould be understood that a multiple syringe pump with two syringes, orany number of syringes, may be used in accordance with the invention.

In various embodiments, fluid 128, such as conductive fluid, can also beprovided from an intravenous (IV) bag full of saline (e.g. of fluidsource 130) that flows under the force of gravity. In such a manner, thefluid 128 may flow directly to device 10, or first to the pump 134located there between. In other embodiments, fluid 128 from a fluidsource 130, such as an IV bag, can be provided through a flow ratecontroller 144 which directly acts on controlling the flow of fluid 128,rather than indirectly by means of pump 134. Such a flow rate controller144 may provide a predetermined flow rate Q by adjusting the crosssectional area of a flow orifice (e.g. lumen of fluid line such as 44 or132) while also sensing the flow rate Q with a sensor such as an opticaldrop counter. Furthermore, fluid 128 from a fluid source 130, such as anIV bag, an be provided through automatically or manually adjusting flowrate controller 144, such as a roller clamp (which also adjusts thecross sectional area of a flow orifice such as lumen of fluid line 44 or132) and is adjusted manually by, for example, the user of device 10 inresponse to their visual observation that the fluid rate Q needsadjustment.

Similar pumps can be used in connection with the invention, and theillustrated embodiments are exemplary only. The precise configuration ofthe pump 134 is not critical to the invention. For example, pump 134 mayinclude other types of infusion and withdrawal pumps. Furthermore, pump134 may comprise pumps which may be categorized as piston pumps, rotaryvane pumps (e.g. axial impeller, centrifugal impeller), cartridge pumpsand diaphragm pumps. In some embodiments, the pump 134 can besubstituted with any type of flow controller, such as a manual rollerclamp used in conjunction with an IV bag, or combined with the flowcontroller to allow the user to control the flow rate of conductivefluid to the device. Alternatively, a valve configuration can besubstituted for pump 134.

In various embodiments, other configurations of the system can be usedwith device 10, and the illustrated embodiments are exemplary only. Forexample, the fluid source 130, pump 134, generator 136, powermeasurement device 140 or flow rate controller 144, or any othercomponents of the system not expressly recited above, may comprise aportion of the device 10. For example, in one exemplary embodiment thefluid source 130 may comprise a compartment of the device 10 whichcontains fluid 128, as indicated at reference character 130 a. Inanother exemplary embodiment, the compartment may be detachablyconnected to device 10, such as a canister which may be attached viathreaded engagement with the device 10. In yet another exemplaryembodiment, the compartment may be configured to hold a pre-filledcartridge of fluid 128, rather than the fluid directly.

Also for example, with regards to alternatives for the generator 136, anenergy source, such as a direct current (DC) battery used in conjunctionwith inverter circuitry and a transformer to produce alternating currentat a particular frequency, may comprise a portion of device 10, asindicated at reference character 136 a. In one embodiment the batteryelement of the energy source may comprise a rechargeable battery. In yetanother exemplary embodiment, the battery element may be detachablyconnected to device 10, such as for recharging.

Turning to FIG. 7, upon being connected to generator 136 and fluidsource 130, fluid 128 is expelled from side flow passage fluid exitopenings 96 a, 98 a, 96 b, 98 b. Fluid 128 expelled from the side flowpassage fluid exit openings 96 a, 98 a, 96 b, 98 b preferably forms athin film coating on surfaces 76 a, 78 a, 76 b, 78 b of electrodes 64 a,66 a, 64 b, 66 b. Excess fluid 128 may flow partially around to thebackside surfaces 120 a, 120 b and form a droplet 154 which subsequentlyfalls and separates from device 10, preferably from drip edges 124 a,124 b. Fluid 128 preferably is inhibited from locating on surfaces 62 a,62 b as already described herein.

As shown in FIG. 7, when device 10 is introduced to tissue 156,typically a surgeon will grasp a small amount of tissue 156, shown hereas a vessel with a lumen 158, and compress the tissue 156 between thegrasping surfaces 62 a, 62 b of the jaws 16 a, 16 b. Where the tissueincludes a lumen 158, such as the lumen of a blood vessel, the lumenwill generally become occluded. Substantially simultaneously with thesurgeon's manipulation of the tissue 156, fluid 128 is continuouslybeing expelled from the side flow passage fluid exit openings 96 a, 98a, 96 b, 98 b.

Fluid 128 expelled from the side flow passage flow exit openings 96 a,98 a, 96 b, 98 b couples tissue 156 and electrodes 64 a, 66 a, 64 b, 66b. As shown in FIG. 7, fluid couplings 160, 162, 164 comprise discrete,localized webs, and more specifically triangular shaped webs. Fluidcouplings 160, 162, 164 provide localized wells of fluid 128 whichenhance the electrical coupling of tissue 156 and electrodes 64 a, 66 a,64 b, 66 b and remove heat generated in tissue 156 by convection.Furthermore, as discussed in greater detail below, couplings 160, 162,164 provide a diversion there through for at least a portion of theelectrical current flowing in tissue 156 outside grasping surfaces 62 a,62 b, whereby the amount of electrical energy available to be convertedinto heat in tissue 156 outside grasping surfaces 62 a, 62 b may becorrespondingly reduced. Additionally, couplings 160, 162, 164 provide alubricant which lubricates the interface between surfaces 76 a, 78 a, 76b, 78 b of electrodes 64 a, 66 a, 64 b, 66 b and surfaces 166 a, 166 bof tissue 156 which inhibits sticking between electrodes 64 a, 66 a, 64b, 66 b and tissue 156 electrically coupled therewith.

Continuing with FIG. 7, as shown the fluid couplings 160, 162, 164 arelaterally outside grasping surfaces 62 a, 62 b of the jaws 16 a, 16 b.Turning to fluid couplings 160 specifically, as shown they are laterallypositioned between a portion of surfaces 76 a, 78 a, 76 b, 78 b ofelectrodes 64 a, 66 a, 64 b, 66 b and grasping surfaces 62 a, 62 b ofthe jaws 16 a, 16 b along outer perimeter edges 125 a, 125 b. Giventheir location, in addition to the benefits of electrical coupling,fluid couplings 160 remove heat from and cool the portion of tissue 156laterally adjacent grasping surfaces 62 a, 62 b and also cool supportmembers 58 a, 58 b along side surfaces 121 a, 121 b thereof.

As shown in FIG. 7, in order to provide fluid 128 at fluid couplings160, preferably a portion of the flow of fluid 128 is provided fromcertain of the side fluid flow passages 92 a, 94 a, 92 b, 94 bconfigured to direct fluid 128 to that portion of tissue 156 that islaterally adjacent grasping surfaces 62 a, 62 b.

Turning fluid couplings 162, as shown in FIG. 7, they are positionedlaterally relative to surfaces 76 a, 78 a, 76 b, 78 b of electrodes 64a, 66 a, 64 b, 66 b. Given their location, in addition to the benefitsof electrical coupling, fluid couplings 162 remove heat and cool theportion of tissue 156 laterally adjacent electrodes 64 a, 66 a, 64 b, 66b. As shown in FIG. 7, in order to provide fluid 128 at fluid couplings162, preferably a portion of the flow of fluid 128 is provided fromcertain of the side fluid flow passages 92 a, 94 a, 92 b, 94 bconfigured to direct fluid 128 to that portion of tissue 156 that islaterally adjacent electrodes 64 a, 66 a, 64 b, 66 b.

Turning to fluid couplings 164, unlike fluid couplings 160 and 162,fluid couplings 164 are not configured to cool tissue 156. Rather, fluidcouplings 164 are configured to remove heat and cool support members 58a, 58 b and base portions 60 a, 60 b of jaws 16 a, 16 b. As shown inFIG. 7, in order to provide fluid 128 at fluid couplings 164, preferablya portion of the flow of fluid 128 is provided from certain of the sidefluid flow passages 92 a, 94 a, 92 b, 94 b configured to direct fluid128 to support members 58 a, 58 b and base portions 60 a, 60 b of jaws16 a, 16 b.

Surfaces 166 a, 166 b of tissue 156 are often uneven or undulated withmicroscopic peaks and valleys. Without fluid 128, the area of electricalcoupling of tissue 156 to the surfaces 76 a, 78 a, 76 b, 78 b ofelectrodes 64 a, 66 a, 64 b, 66 b can be limited to the isolated peaksin the tissue surfaces 166 a, 166 b. In this situation, upon theapplication of RF energy to tissue 156, the electrical coupling area ofsurfaces 166 a, 166 b, by virtue of being limited to the tissue peaks,results in corresponding increase in current density through the peakswhich has the ability to desiccate and char the tissue 156. Conversely,fluid 128 enters and occupies the previously unoccupied valleys and gaps167 (as shown in FIG. 8) between tissue surfaces 166 a, 166 b and thesurfaces 76 a, 78 a, 76 b, 78 b of electrodes 64 a, 66 a, 64 b, 66 b andenhances the electrical coupling of the tissue surfaces 166 a, 166 b tothe surfaces 76 a, 78 a, 76 b, 78 b of electrodes 64 a, 66 a, 64 b, 66b.

Furthermore, the intimacy of electrical coupling between surfaces 166 a,166 b of tissue 156 and the surfaces 76 a, 78 a, 76 b, 78 b ofelectrodes 64 a, 66 a, 64 b, 66 b often decreases as the tissue shrinksaway from surfaces 76 a, 78 a, 76 b, 78 b and/or desiccates duringtissue treatment conversely, fluid 128 provides a mechanism to offsetlosses in electrical coupling due to tissue shrinkage and/or desiccationby entering and occupying any gaps 167 (as shown in FIG. 8) which havedeveloped between surfaces 166 a, 166 b of tissue 156 and the surfaces76 a, 78 a, 76 b, 78 b of electrodes 64 a, 66 a, 64 b, 66 b duringtreatment.

Once the jaws 16 a, 16 b are closed to a use position, RF power is thenprovided to the tissue 156. RF power is provided at the tissue surface166 a, 166 b and below the tissue surface 166 a, 166 b into the tissue156 directly from electrodes 64 a, 66 a, 64 b, 66 b, as well as throughthe fluid couplings 160 and 162 to a targeted tissue treatment site,here between grasping surfaces 62 a, 62 b, thereby heating the tissue156 to coagulate, shrink, weld or otherwise treat the tissue 156.

If desired, after treating the tissue 156 between the jaws 16 a, 16 b,the jaws 16 a, 16 b can be held clamped together and cutting mechanism32 can be actuated to cut the tissue 156. As shown in FIG. 5, cuttingmechanism 32 preferably comprises a cutting blade with a sharpeneddistal end. Preferably cutting mechanism 32 is actuated by rotatingpaddles 30 distally to longitudinally extend the blade distally andthereafter rotating the paddles 30 proximally to longitudinally retractthe cutting blade proximally.

In order to reduce tissue treatment time, lateral thermal spread andensuing necrosis of tissue 156 laterally outside grasping surfaces 62 a,62 b, particularly tissue 156 laterally adjacent grasping surfaces 62 a,62 b, adjacent the electrodes 64 a, 66 a, 64 b, 66 b and there inbetween, it is desirable to concentrate the energy to the tissue 156between grasping surfaces 62 a, 62 b of device 10 as shown below as partof the present invention. Before continuing, however, it should be notedthat the examples below should only be considered to an order ofmagnitude approximation for explanatory purposes.

Electrical resistance R_(e) to the passage of RF current can bedescribed by equation (1) below:R _(e)=ρ_(e) L/A  (1)

where:

R_(e)=electrical resistance (ohms);

ρ_(e)=electrical resistivity (ohm-cm);

L=length (cm); and

A=area (cm²).

In determining the electrical resistance of tissue R_(et) locatedbetween surfaces 62 a, 62 b of device 10, the length of tissue L isrepresented by the width across surfaces 62 a, 62 b of jaws 16 a, 16 b.The area A of the tissue is represented by a longitudinal dimension ofsurfaces 62 a, 62 b and the thickness of tissue between surfaces 62 a,62 b. In other words, with reference to FIGS. 5 and 10 for dimensions a,b and c, the electrical resistance of tissue R_(et) located betweensurfaces 62 a, 62 b using equation (1) is expressed as:R _(et (between grasping surfaces))=ρ_(et) b/ac  (2)

By way of example, where the tissue 156 located between surfaces 62 a,62 b of device 10 has a dimension a of 0.025 cm, a dimension b of 0.3cm, a dimension c of 3 cm and an electrical resistivity of the tissueρ_(et) of 200 ohm-cm before treatment, the electrical resistance of thetissue R_(et) between surfaces 62 a, 62 b of device 10 is about 800ohms.

Conversely, for tissue 156 adjacent electrodes 64 a, 66 a, 64 b, 66 b,equation (1) is expressed as:R _(et (adjacent the electrodes))=ρ_(et) a/bc  (3)

Note that the area A of tissue 156 is now measured by the product of(b)(c). For tissue 156 adjacent electrodes 64 a, 66 a, 64 b, 66 b,dimension b comprises the portion of the circumference of the electrodes64 a, 66 a, 64 b, 66 b electrically coupled to tissue 156. Thus, asshown in FIG. 10, dimension b can be approximated by about one-quarterof the circumference of electrodes 64 a, 66 a, 64 b, 66 b. Consequently,where the diameter of electrodes 64 a, 66 a, 64 b, 66 b is 0.15 cm,dimension b is about 0.1 cm for each electrode. Next, when dimension cis held constant (i.e. 3 cm), area A for each electrode 64 a, 66 a, 64b, 66 b is about 0.3 cm².

In the case of four electrodes with the electrical potential andpositioning such as electrodes 64 a, 64 b and 66 a, 66 b, the electricalresistance of the tissue R_(et) adjacent electrodes 64 a, 64 b and 66 a,66 b could be considered in parallel. However, in order to assume aworse case scenario, as well as simply the system, the existence of onlytwo electrodes (e.g. 64 a, 66 b) will be assumed in continuing with thecalculations herein.

Turning to dimension a, as shown in FIG. 10 electrodes 64 a, 66 b arerecessed relative to surfaces 62 a, 62 b. Dimension a relative toelectrodes 64 a, 66 b can be somewhat arbitrarily estimated as beingabout twice dimension a between surfaces 62 a, 62 b. Thus, using adimension a of 0.05 cm, and keeping the electrical resistivity of thetissue ρ_(et) constant at 200 ohm-cm, the electrical resistance of thetissue R_(et) adjacent the electrodes 64 a, 66 b is about 33 ohms. Thus,the above illustrates that the electrical resistance of the tissueR_(et) adjacent electrodes 64 a, 66 b can be substantially lower thanthe electrical resistance of the tissue R_(et) between surfaces 62 a, 62b.

The total electrical resistance R_(eTotal) encountered in an electricalcircuit for resistors in series can be approximated by adding theelectrical resistance of each resistor in the circuit. Thus, for theexample above, the total electrical resistance R_(eTotal) may beapproximated as 866 ohms. Continuing with the above, assuming a power Pof 35 watts and a total electrical resistance R_(eTotal) is 866 ohms,from Ohm's Law the current I is about 0.2 amps. In turn, also from Ohm'sLaw the amount of the power P converted to heat in the tissue 156located between surfaces 62 a, 62 b of device 10 is about 32 watts whilethe power P converted into heat in the tissue 156 adjacent electrodes 64a, 66 b is about 3 watts. Stated another way, about 90% of the power isconverted to heat in the resistance of the tissue 156 located betweensurfaces 62 a, 62 b of device 10.

Once the current I flowing through tissue 156 is known, the currentdensity in tissue 156 may also be calculated. Current density is avector quantity whose magnitude is the ratio of the magnitude of currentI flowing through a substance to the cross-sectional area Aperpendicular to the current direction of flow and whose directionpoints in the direction of the current flow. Current density is commonlyexpressed in amperes per square centimeter (i.e. amps/cm²).

In light of the above definition, the current density in tissue 156between surfaces 62 a, 62 b of device 10 when using an area A of 0.075cm² (i.e. dimension a of 0.025 cm and dimension c of 3 cm) as above isabout 2.7 amps/cm². Conversely, the current density in tissue 156adjacent electrodes 64 a, 66 b when using an area A of 0.3 cm² as aboveis about 0.6 amps/cm². Thus, the current density in tissue 156 betweensurfaces 62 a, 62 b of device 10 is on a magnitude of 4 times greaterthan the current density in tissue 156 adjacent electrodes 64 a, 66 a,64 b, 66 b for the preceding example.

In certain instances, use of device 10 may result in a load impedanceoutside the working range of a general-purpose generator 136. Forexample, the schematic graph of FIG. 11 shows the general output curveof a typical general-purpose generator, with the output power changingas load (tissue plus cables) impedance Z changes. Load impedance Z (inohms) is represented on the X-axis, and generator output power P (inwatts) is represented on the Y-axis. In the illustrated embodiment, theelectrosurgical power (RF) is set to 75 watts in a bipolar mode.

As shown in FIG. 11, the power P will remain constant as it was set aslong as the impedance Z stays between two cut-offs, low and high, ofimpedance, that is, for example, between 50 ohms and 300 ohms in theillustrated embodiment. Below load impedance Z of 50 ohms, the power Pwill decrease, as shown by the low impedance ramp 168. Above loadimpedance Z of 300 ohms, the power P will decrease, as shown by the highimpedance ramp 170. This change in output is invisible to the user ofthe generator and not evident when the generator is in use, such as inan operating room.

As shown by the exemplary calculations above, the high impedance cut-offwhere power P begins to decrease as shown by high impedance ramp 170 maybe exceeded with use of device 10 and quite possibly be completelyoutside the working range of generator 136. Consequently, as shown inFIG. 9, it may be necessary to provide an impedance transformer 172 in aseries circuit configuration between electrodes 64 a, 66 a, 64 b, 66 bof device 10 and the power output of generator 136. Consequently, theimpedance transformer 172 may be provided with device 10, the generator136 or any of the wire connectors (e.g. cable 34) connecting device 10and generator 136. Impedance transformer 172 is configured to match theload impedance provided to generator 136 such that it is within theworking range of the generator 136 and, more preferably in the workingrange between the low and high cut-offs.

As already described herein, an exemplary electrical resistivity of thetissue ρ_(et) is about 200 ohm-cm. Also as already described herein, forsaline the electrical resistivity of the fluid ρ_(ef) is about 50 ohm-cmfor physiologic saline and about 5 ohm-cm for hypertonic saline. Thus,the electrical resistivity of the tissue ρ_(et) for the present exampleis about four times to forty times greater than the electricalresistivity of the fluid ρ_(ef). Consequently, assuming all else equal,electrical current I will flow more predominately through the conductivefluid 24 rather than through tissue 32. The position of fluid couplings160 is configured for this and exploits it.

As electrical current flows in the tissue 156 between surfaces 62 a, 62b and exits from between surfaces 62 a, 62 b, it will seek a path to thecounter electrode comprising the least electrical resistance R_(e). Asalready discussed herein, among other things, electrical resistanceR_(e) is a function of electrical resistivity ρ_(e) and length L of theresistor. In the case of physiologic saline, the electrical resistivityof the conductive fluid ρ_(ef) making up fluid couplings 160 isone-fourth the electrical resistivity of the tissue ρ_(et). Furthermore,as shown in FIG. 7, the shortest distance for the electrical current Ito travel to the counter electrode upon exiting from between surfaces 62a, 62 b is through fluid couplings 160. An exemplary distance betweenthe edges 125 a, 126 b to surfaces 62 a, 62 b and the closest portion ofan electrode surface 76 a, 76 b, 78 a, 78 b thereto is in the rangebetween and including about 0.5 mm to 5.0 mm. More preferably, thedistance between the edges 125 a, 126 b to surfaces 62 a, 62 b and theclosest portion of an electrode surface 76 a, 76 b, 78 a, 78 b is in therange between and including about 1 mm to 3.0 mm.

Consequently, electrosurgical device 10 and the system is configured toprovide a diversion for (and preferably divert at least a portion of)electrical current, upon exiting from between grasping surfaces 62 a, 62b, to flow at least partially through conductive fluid 128 beforereaching the counter electrode. In other words, couplings 160 and 162provide a diversion there through for at least a portion of theelectrical current flowing in tissue 156 outside grasping surfaces 62 a,62 b, whereby the amount of electrical energy available to be convertedinto heat in tissue 156 outside grasping surfaces 62 a, 62 b may becorrespondingly reduced.

Similar to the counter electrode side of the electrical path, aselectrical current flows from the source electrodes and enters betweensurfaces 62 a, 62 b it will also seek a path to the counter electrodecomprising the least electrical resistance R_(e). Consequently, inaddition to the above, device 10 and the system are also configured toprovide a diversion for (and preferably divert at least a portion of) atleast a portion of the electrical current, upon leaving the sourceelectrode, at least partially through conductive fluid 128 beforeentering between grasping surfaces 62 a, 62 b.

In light of the above, it may be desirable to increase the size (i.e.volume and area) of the fluid coupling between tissue 156 and theelectrodes 64 a, 66 a, 64 b, 66 b. More specifically, preferably thejaws 16 a, 16 b are configured such that tissue 156 is inhibited fromdirect contact with the electrodes 64 a, 66 a, 64 b, 66 b. Referring toFIGS. 12 and 13, a stand-off 174, here a separator which holds twobodies separate from one another preferably at a predetermined distance,inhibits the tissue 156 from direct contact with surfaces 76 a, 78 a, 76b, 78 b of electrodes 64 a, 66 a, 64 b, 66 b.

As shown, stand-off 174 preferably comprises a coil, preferablycomprising electrically insulated surfaces, superimposed (overlying) andwrapped around the electrode surfaces 76 a, 78 a, 76 b, 78 b, thusproviding a helical flow channel 177 between bordering windings of thecoil. As a result, fluid couplings 160 and 162 merge in a new fluidcoupling shown at 176. Fluid coupling 176, by virtue of its increasedsize, provides an even greater diversion than fluid-coupling 160 for atleast a portion of the electrical current flowing in tissue 156 outsidegrasping surfaces 62 a, 62 b consequently, further reduces the amount ofelectrical energy available to be converted into heat in tissue 156outside grasping surfaces 62 a, 62 b.

Preferably the electrically insulative surfaces of the coil are providedby the coil being formed of an electrically insulative material, such asa polymer. For assembly, preferably each electrode 64 a, 66 a, 64 b, 66b is passed through the center longitudinal aperture of a coil, with thecoil wrapped around and extending along the length of the surfaces 76 a,78 a, 76 b, 78 b of electrodes 64 a, 66 a, 64 b, 66 b between the distaland proximal connector portions of jaws 16 a, 16 b which connect theelectrodes 64 a, 66 a, 64 b, 66 b to the jaws 16 a, 16 b.

In yet another embodiment, the stand-off may comprise a materialpervious to the passage of fluid 128 therethrough. As shown in FIG. 14,stand-off 175 may comprise a porous structure which includes a pluralityof tortuous and interconnected fluid flow passages which provide anddistribute fluid 128 to tissue 156.

Similar to stand-off 174, preferably stand-off 175 comprises aelectrically insulative material, such as a polymer or ceramic,superimposed over the electrode surfaces 76 a, 78 a, 76 b, 78 b. With anelectrically insulative porous structure, RF energy is provided totissue 156 through the electrically conductive fluid 128 containedwithin the plurality of interconnected tortuous pathways rather than theporous material itself. A porous polymer structure may be provided by acellular solid comprising interconnected voids which define the tortuousand interconnected passages. For example, the porous polymer structuremay comprise a polymer foam at least partially comprising an opencellular structure. Furthermore, in certain embodiments, the stand-off175 may comprise a compressible, resilient structure, such as providedby a flexible or semi-rigid polymer foam. In this manner, the stand-off175 can deform around tissue 156 to provide better electrical and fluidcoupling therewith.

In certain embodiments, the electrodes 64 a, 66 a, 64 b, 66 b may alsocomprise a material previous to the passage of fluid 128 therethrough,such as a porous metal. The discrete, linear side flow passages 92 a, 94a, 92 b, 94 b may be either supplemented with or replaced by a pluralityof tortuous, interconnected pathways formed in the porous materialwhich, among other things, provide porous electrode surfaces 76 a, 78 a,76 b, 78 b which more evenly distribute fluid flow and provide fluid 128to tissue 156.

Preferably the porous materials provide for the wicking (i.e. drawing inof fluid by capillary action or capillarity) of the fluid 128 into thepores of the porous material. In order to promote wicking of the fluid128 into the pores of the porous material, preferably the porousmaterial, and in particular the surface of the tortuous pathways, ishydrophilic. The porous material may be hydrophilic with or without posttreating (e.g. plasma surface treatment such as hypercleaning, etchingor micro-roughening, plasma surface modification of the molecularstructure, surface chemical activation or crosslinking), or madehydrophilic by a coating provided thereto, such as a surfactant.

As described herein, in order that heat may be transferred away fromsurfaces 62 a, 62 b during use of device 10, preferably the material forsupport members 58 a, 58 b particularly the medial portion of supportmembers 58 a, 58 b adjacent surfaces 62 a, 62 b) and base portions 60 a,60 b have a high thermal conductivity. As shown above, given that thevast amount of the power provided to tissue 156 is converted to heat inthe tissue 156 between surfaces 62 a, 62 b of device 10, it may benecessary to configure support members 58 a, 58 b and bases 60 a, 60 bsuch that surfaces 62 a, 62 b do not overheat. However, support members58 a, 58 b and bases 60 a, 60 b should be also configured such thatsurfaces 62 a, 62 b do not overcool. Preferably, during a typical use ofdevice 10, surfaces 62 a, 62 b should remain in the temperature rangebetween and including about 75° C. to 120° C. More preferably, duringuse of device 10, surfaces 62 a, 62 b should remain in the temperaturerange between and including about 75° C. to 100° C. Stated another way,surfaces 62 a, 62 b should be hot enough to shrink collagen in the rangebetween and including about 1 second to 10 seconds after RF activation.

As shown in FIG. 11, RF power to tissue can vary even though thegenerator 136 has been “set” or “fixed” to a particular wattage. FIG. 15shows an exemplary schematic graph that describes one relationshipbetween the flow rate Q of fluid 128 (Y-axis in cc/min.) versus RF powerP to tissue 156 (X-axis in watts). More precisely, as shown in FIG. 15,the relationship between the rate of fluid flow Q and RF power P may beexpressed as a direct, linear relationship, when a steady-statecondition has been achieved (temperature not changing with time).

Based on a simple, one-dimensional, steady-state, lumped parameter modelof the heat transfer and a predetermined peak tissue temperature, theflow rate Q of fluid 128 corresponding to the peak tissue temperaturecan be determined. The RF electrical power P that is converted into heatcan be defined as:P=ρ_(m)c_(ρ)Q₁ΔT  (4)where P=the RF electrical power that is converted into heat. The term[ρ_(m)c_(ρ)Q₁ΔT] in equation (4) is heat used to warm up the flow offluid 128 to peak temperature (without boiling the fluid), where:

-   -   ρ_(m)=Density of the fluid (approximately 1.0 gm/cm³ for        physiologic saline);    -   c_(ρ)=Specific heat of fluid (approximately 4.1 watt-sec/gm-° C.        for physiologic saline);    -   Q₁=Flow rate of the fluid that is heated (cm³/sec); and    -   ΔT=Temperature rise of the fluid. The difference in temperature        between the peak fluid temperature and the initial (input) fluid        temperature. The inlet fluid temperature is typically at ambient        temperature or about 20° C. for a hospital operating room.

Assuming that the peak fluid temperature is the same as the peak tissuetemperature at steady state, the flow rate for a predetermined peakfluid temperature (provided the temperature is at or below boiling ofthe fluid) can be determined by solving equation (4) for Q₁:Q ₁ =[P]/ρ _(m) c _(ρ) ΔT  (5)

This equation defines the lines shown in FIG. 15 with a slope given by1/(ρ_(m)c_(p)ΔT). Assuming an inlet temperature of 20° C., FIG. 15 showsseveral lines for different outlet temperatures of 45, 50, 60 and 100°C.

Outside of surfaces 62 a, 62 b it is desirable to provide a tissuetemperature which inhibits tissue necrosis. The onset of tissue necrosiswill generally occur at about 60° C. with an exposure time of about 0.02seconds. As temperature decreases, the time for tissue necrosisincreases. For a tissue temperature of about 45° C., exposure timeincreases to about 15 minutes. Thus, an exemplary targeted steady statetemperature is about 50° C.

Worse case, assuming all the power to tissue (i.e. here 35 watts) has tobe removed by fluid 128 after the jaws 16 a, 16 b and fluid 128 havereached a targeted steady state temperature of 50° C., the calculatedflow rate Q is [35]/(1)(4.1)(50−20)=0.28 cc/sec or about 17 cc/min.

It should be understood that the flow rate Q above is merely exemplary.An exemplary range of flow rates for device 10 is from about 0.01cc/min. to about 100 cc/min.

In light of the above, an exemplary control strategy which can beemployed for the device 10 is to provide a flow rate Q of fluid 128 toinhibit necrosis of tissue 156 outside surfaces 62 a, 62 b which may besubject to necrosis by the portion of the total power P provided totissue 156 outside surfaces 62 a, 62 b.

In order to determine when a predetermined temperature of the fluid 128has been achieved (e.g., when the fluid reaches, for example, 50° C.), athermochromic material (a material that changes color as it is heated orcooled), such as a thermochromic dye (e.g., leuco dye), may be added tothe fluid. The dye can be formulated to provide a first predeterminedcolor to the fluid at temperatures below a predetermined temperature,such as 50° C., then, upon heating above 50° C., the dye provides asecond color, such as clear, thus turning the fluid clear (i.e. no coloror reduction in color). This color change may be gradual, incremental,or instant. Thus, a change in the color of the fluid, from a first colorto a second color (or lack thereof) provides a visual indication to theuser of the electrosurgical device 5 as to when a predetermined fluidtemperature has been achieved. Thermochromic dyes are available, forexample, from Color Change Corporation, 1740 Cortland Court, Unit A,Addison, Ill. 60101.

In some embodiments, it can be desirable to control the temperature ofthe fluid 128 before it is released from the device 10. In oneembodiment, a heat exchanger is provided for the outgoing fluid flow toeither heat or chill fluid 128. The heat exchanger may be provided aspart of device 10 or as part of another part of the system, such aswithin the enclosure 152. Cooling the fluid 128 to a predeterminedtemperature, typically below room temperature, further inhibits thermaldamage to tissue outside surfaces 62 a, 62 b. More specifically, the useof chilled saline (i.e. below room temperature of about 20° C. and ofany salt concentration) will inhibit tissue damage outside surfaces 62a, 62 b due to heat conduction. Flowing fluid 128 will absorb the heatfrom higher temperature tissue, dilute it with the cooler fluid 128 andremove it from the device 10. Chilling and convective cooling should notsignificantly affect the amount of resistance heating except by slightlyincreasing the electrical resistivity for saline and chilled tissue.Chilling and convective cooling with the fluid 128 will simply reducethe peak temperatures that are created in the tissue outside surfaces 62a, 62 b.

In other embodiments, as shown in FIG. 16, electrodes 64 a, 66 a, 64 b,66 b may be located at least partially directly beneath surfaces 62 a,62 b. Consequently, with such a configuration, heat transfer fromsupport members 58 a, 58 b and surfaces 62 a, 62 b may be furtherincreased. As shown, support members 58 a, 58 b, particularly theportion underlying surfaces 62 a, 62 b, are convection cooled by flowingfluid 128 provided from side flow passages 92 a, 94 a, 92 b, 94 b ofelectrodes 64 a, 66 a, 64 b, 66 b. Furthermore, the support members 62a, 62 b are also cooled via conduction of heat to the portions ofelectrodes 64 a, 66 a, 64 b, 66 b in direct contact therewith. This heatis then transferred via conduction through electrodes 64 a, 66 a, 64 b,66 b to flowing fluid 124 contained within central fluid flow passage 84a, 86 a, 84 b, 86 b where it is carried away through side flow passages92 a, 94 a, 92 b, 94 b.

Preferably device 10 is provided with a means to inform the use of thedevice when tissue between surfaces 62 a, 62 b has been sufficientlycoagulated. As known in the art, with the application of RF powerthrough tissue its impedance changes. As shown by Bergdahl, theelectrical impedance of tissue initially decreases (to an impedancevalue below its initial untreated impedance value) and then subsequentlyincreases as the tissue desiccates and coagulates. (Bergdahl, J.Neurosurg., Vol. 75, July 1991, pages 148-151). Correspondingly, in aconstant voltage situation and by virtue of Ohm's law, the electricalcurrent through the tissue initially increases (as tissue impedancedecreases) and then decreases (as tissue impedance increases). Thus, theelectrical current in the tissue is inversely proportional to theimpedance.

However, prior art electrosurgical devices such as device 10 do notindicate the tissue impedance, or provide any visual or audible feedbackas to the state of the tissue being treated at the targeted tissuetreatment site. In a small number of instances, ammeters have been knownto be located on generators, but due to relative location, for examplein a hospital operating room, are not easily usable. Often the generatoris removed from the patient and electrosurgical device, and not viewableby the user of the electrosurgical device without looking away from thesurgical procedure. Consequently, clinical judgment and operatortraining are required to minimize or prevent incomplete coagulation orcharring and sticking from overheating. If an under treated vessel istransected or cut, it may bleed or worse leak, often after the surgicalincision is closed.

An advancement of the art would be to provide direct information whencoagulation or other tissue treatment is completed, preferably such thatthe surgeon or other user of the electrosurgical device would beinformed of the completion of tissue treatment while still lookingtowards the surgical procedure/patient and viewing the indicator withinthe their vision, either direct or indirect (peripheral) vision. Suchwould be particularly useful for laparoscopic surgery, particularly ifthe information was provided to the user of the device while viewing theperitoneal cavity.

As shown in FIGS. 1 and 9, in order for the operator or other user ofdevice 10 to gauge the level of treatment for tissue 156 betweensurfaces 62 a, 62 b device 10 may be provided with a tissue treatmentindicator 184. Preferably the tissue treatment indicator 184 providesthe user of device 10 with a visual output related to the level oftreatment for tissue 156 between surfaces 62 a, 62 b. In one embodiment,the visual indicator preferably comprises a lighting device (e.g.incandescent bulb, halogen bulb, neon bulb). In another embodiment, thevisual indicator preferably comprises a thermochromic device.

As shown in FIG. 9, for example, the present invention may use anincandescent bulb or thermochromic strip wired in parallel circuitconfiguration with a power feed line (e.g. wire conductor 40 ofinsulated wire 36 of cable 34) providing power to electrodes 64 a, 66 a,64 b, 66 b of device 10 from generator 136. Consequently, the tissuetreatment indicator 184, here comprising an incandescent bulb orthermochromic strip, may be provided with device 10 (as shown), thegenerator 136 or any of the wire connectors (e.g. cable 34) connectingdevice 10 and generator 136.

More specifically, as shown in FIG. 9, the incandescent bulb orthermochromic strip is preferably wired in parallel circuit with a shortsection of wire conductor 40 (e.g. between about 1 cm and 60 cm ofinsulated wire 36 of cable 34) within the confines of device 10 andmounted on device 10, such as on handle 22 or preferably the tip portion14 (as shown in FIG. 1). Preferably the indicator 184 is mounted to thetip portion 14 of device 10 such that when the tip portion 14 isinserted into the peritoneal cavity, or other cavity, the indicator 184is visible within the confines of the peritoneal cavity by a surgeonusing a laparoscopic viewing scope or camera as known in the art.

During use of device 10, the brightness and change in brightness of theindicator 184 during tissue coagulation can be used to indicate thelevel of coagulation and consequent coaptation of a vessel and tissuestructure. More specifically, as the tissue impedance decreasesinitially, the indicator will increase in brightness (with increasingcurrent) and thereafter decrease in brightness (with decreasing current)as the tissue impedance increases.

As shown in FIG. 11, the power P from generator 136 will remain constantas long as the impedance Z stays between a low impedance cut-off 168 anda high impedance cut-off 170. As indicated above, transformer 172 isconfigured to match the load impedance provided to generator 136 suchthat it is within the working range of the generator 136 and, morepreferably in the working range between the low impedance cut-off 168and high impedance cut-off 170.

Upon the application of device 10 to tissue, generally impedance willinitially reside within the generator's working range between the lowimpedance cut-off 168 and high impedance cut-off 170. Before tissue istreated in any significant manner, the indicator 184 will provide afirst brightness level which is representative of a first impedancelevel.

For a period thereafter, the tissue impedance decreases. From Ohm's law,the change in impedance (here decrease) over a constant power P outputfrom generator 136 will result in a change in the current I (hereincrease) of the circuit. As the current increases, the brightness ofthe indicator 184 will correspondingly increase to a second brightnesslevel which is representative of a second impedance level.

After reaching a minimum tissue impedance, the tissue impedance willchange direction and begin to increase with tissue coagulation anddesiccation. Here, the change in impedance (here increase) over aconstant power P output from generator 136 will result in a change inthe current I (here decrease) of the circuit. As the current decreases,the brightness of the indicator 184 will correspondingly decrease to athird brightness level which is representative of a third impedancelevel.

Thus from the above configuration, one would see current changesmirroring the tissue impedance changes. If the bulb (e.g. a tungstenfilament type #47 or equivalent) were placed across a 1-foot segment ofthe power cable, the lamp brightness would provide visual indication ofcurrent. The lamp will glow brightly when device 10 is activated and theelectrodes are in good contact with the tissue. Subsequently, there willbe a marked decrease in brightness or dimming of the lighted bulb ascoagulation advances and is completed.

The jaw configurations described above may be particularly useful foruse through a 12 mm or greater diameter trocar cannula. In still otherembodiments, the jaws may be configured to use through a 3 mm, 5 mm, 10mm or greater diameter trocar cannula. As shown in FIG. 17, in order toreduce size and complexity, the two electrodes from jaw 16 a have beeneliminated (i.e. 64 a, 66 a). Furthermore, as shown, preferably the tworemaining electrodes, here 64 b, 66 b, are located on the same jaw 16 b.Furthermore, the cutting mechanism 32 and the base 60 a have also beeneliminated. Also as shown, jaw 16 a is configured substantiallyasymmetrical to jaw 16 b and has a much flatter profile. In this manner,jaws 16 a, 16 b may function as tissue dissectors. In other words, whilejaws 16 a, 16 b are in the closed position and without tissue therebetween, they are wedged into tissue, preferably between adjacent tissueplanes. Thereafter, the jaws 16 a, 16 b may be slowly opened and, due tothe separation forces placed on the tissue at the distal end 56 of thejaws 16 a, 16 b, the tissue will dissect.

FIGS. 18-21 show another embodiment of the present invention with themedial portion of the backside surfaces 120 a, 120 b of jaws 16 a, 16 bcomprising a substantially flat surface as opposed to the arcuatesurface of previous embodiments.

Thus far the device 10 has been described relative to use with anendoscopic grasper, and in particular endoscopic forceps. In still otherembodiments, as shown in FIG. 22, the present tissue grasper of thepresent invention may comprise an open surgery grasper and moreparticularly open surgery forceps.

Returning to transformer 172, when transformer 172 is provided as partof device 10, such as with cable 34 as shown in FIG. 9, cable 34 ofdevice 10 may ordinarily comprise two insulated wires 36, 38 connectableto generator 136 via two banana (male) plug connectors 35 a, 35 b (asbest shown in FIG. 1), connecting to (female) plug receptacles 137 a,137 b of the generator 136. As shown in FIG. 1, the banana plugconnectors 35 a, 35 b are each assembled with wires 36, 38 withinindividual plug housings 43 a, 43 b which are not connected relative toone another and may be referred to as “loose leads”. Consequently, inthis embodiment, the banana plug connectors 35 a, 35 b are independentlymovable relative to one another. In this manner, plug connectors 35 a,35 b are not fixed in a predetermined position relative to one anotherand thus may be arranged to connect to a variety generators 136 whichmay have receptacle connectors 137 a, 137 b with different patterns andplacement. Exemplary electrical configurations established betweenbanana plug connectors 35 a, 35 b of device 10 and banana plugreceptacle connectors 137 a, 137 b of generator 136 are furtherillustrated in FIGS. 23 and 24. From the above, it should be understoodthat the use of plug connectors and receptacle connectors, is merelyexemplary, and that other types of mating connector configurations maybe employed.

In other embodiments, transformer 172 may be assembled with wires 36, 38and plug connectors 35 a, 35 b in a single, common housing similar tothe housing 43 shown in FIG. 25. In contrast to the previous embodiment,in this embodiment the plug connectors 35 a, 35 b are held in a fixed,predetermined position relative to one another. In this manner, the plugconnectors 35 a, 35 b can be tailored to fit only those generators 136with receptacle connectors 137 a, 137 b positioned to coincide or matchup with the predetermined positions of the plug connectors 35 a, 35 b.

Plug connectors 35 a, 35 b are provided in a single common housing 43 tobetter and more easily direct the plug connectors 35 a, 35 b to theirpredetermined targeted plug receptacle connectors 137 a, 137 b by virtueof being held in a fixed, predetermined position relative to one anotherby plug housing 43 such that they can only coincide with receptacleconnectors 137 a, 137 b, respectively.

As shown in FIG. 25, the wiring within plug housing 43 of device 10 maybe configured such that hand switch 142 a may be electrically coupled tothe bipolar mode hand switching circuitry of generator 136. Morespecifically, as shown hand switch 142 a of device 10 is electricallycoupled to generator 136 upon the insertion of bipolar hand switch plugconnector 35 c of device 10 into bipolar hand switch receptacleconnector 137 c of generator 136. In other embodiments, the hand switch142 a may be eliminated and foot switch 142 of generator 136 may be usedalone.

In still other embodiments, transformer 172 may be provided as part ofan electrical adaptor 186 connected in series between device 10 andgenerator 136 as shown in FIG. 26. In this embodiment, preferably theadaptor 186 includes its own receptacle connectors 188 a, 188 b on oneside which are configured to receive plug connectors 35 a, 35 b ofdevice 10, and on the opposing side has its own plug connectors 190 a,190 b which are configured to connect to receptacle connectors 137 a,137 b of generator 136.

As shown in FIG. 26, adaptor 186 may also be configured to accommodatedevice 10 with hand switch 142 a. In addition to the various connectorsidentified above, adaptor 186 has its own bipolar hand switch receptacleconnector 188 c on one side configured to mate with the bipolar handswitch plug connector 35 c of device 10, and on the opposing side hasits own bipolar hand switch plug connector 190 c configured to connectto bipolar hand switch receptacle connector 137 c of generator 136.Finally, in order to establish the remaining link between the handswitch circuitry and the bipolar power output, the adaptor 186 has ahand switch plug connector 188 d configured to mate with hand switchreceptacle connector 35 d of device 10.

As shown in FIG. 26, device 10 now includes four connectors (i.e. 35 a,35 b, 35 c, 35 d) when adaptor 186 is used rather than just the threeconnectors (i.e. 35 a, 35 b, 35 c) associated with the embodiment ofFIG. 25. Connector 35 d is added to provide a connection, when matedwith connector 188 d of adaptor 186, to plug connector 190 a whichbypasses transformer 172. This is required as the hand switch circuitryof generator 136 typically utilizes direct current (DC) rather than thealternating current (AC) associated with the power circuitry.Consequently, since continuous DC will not cross between the primarycoil 173 and secondary coil 175 (shown in FIG. 23), of transformer 172,this fourth connection is required.

Turning to the specifics of transformer 172, preferably the transformer172 comprises primary and secondary coils 173, 175 comprising #18 magnetwire wound on a toroidal shaped, magnetic core 179. Primary coil 173receives power from the generator 136 while secondary coil 175 receivesthe power from the primary coil 173 and delivers it to the load. Morepreferably the core 179 comprises a ferromagnetic core and even morepreferably a ferrite core. Preferably the ferrite has an amplitudepermeability in the range of 500μ to 5,000μ and more preferably of about2,000μ. More preferably, the ferrite comprises ferrite material no. 77.

For a perfect transformer, that is, a transformer with a coefficient ofcoupling (k) equal to 1, the impedances can be described as follows:Z _(p) =Z _(s)(N _(p) /N _(s))²  (6)where:

Z_(p)=Impedance looking into the primary coil from the power source;

Z_(s)=Impedance of load connected to secondary coil;

N_(p)=Number of turns (windings) for primary coil; and

N_(s)=Number of turns (windings) for secondary coil

As indicated above, as shown in exemplary FIG. 11, the power P inbipolar mode will remain constant as it was set as long as the impedanceZ stays between two cut-offs, low and high, of impedance, that is, forexample, between 50 ohms and 300 ohms in the illustrated embodiment.Below load impedance Z of 50 ohms, the power P will decrease, as shownby the low impedance ramp 168. Above load impedance Z of 300 ohms, thepower P will decrease, as shown by the high impedance ramp 170.

In light of the above, in bipolar mode the primary impedance Z_(p)should be no greater than 300 ohms. As for secondary impedance Z_(s), asshown above, secondary impedance Z_(s) may be on the order of 900 ohms.Based a primary impedance Z_(p)=300 ohms and a secondary impedanceZ_(s)=900 ohms, the transformer 172 should be a step-up transformer witha turns ratio, N_(p)/N_(s) of 1:1.7.

However, it has been found that for general-purpose generators 136, thehigh impedance cut-off in bipolar mode may occur substantially below 300ohms. It has been found, that for some general-purpose generators 136,the high impedance cut-off may occur at only about 100 ohms. Based aprimary impedance Z_(p)=100 ohms and a secondary impedance Z_(s)=900ohms, the transformer 172 should be a step-up transformer with a turnsratio, N_(p)/N_(s) of 1:3.

It should also be recognized that the above calculations for N_(p)/N_(s)are predicated on an electrical resistivity of the tissue ρ_(et) of 200ohm-cm. However, in certain instances the electrical resistivity of thetissue ρ_(et) can be on the order of about 2500 ohm-cm, for example, forfat tissue. In this situation the electrical resistance of the tissueR_(et) may be on the order of 10,000 ohms. Based a primary impedanceZ_(p)=100 ohms and a secondary impedance Z_(s)=10,000 ohms, thetransformer 172 should be a step-up transformer with a turns ratio,N_(p)/N_(s) of 1:10. When the primary impedance Z_(p) is increased backto 300 ohms for a generator with this high impedance cut-off, thetransformer 172 should be a step-up transformer with a turns ratio,N_(p)/N_(s) of 1:5.8.

More probable than above, the electrical resistivity of the tissueρ_(et) will be on the order of about 1200 ohm-cm, in which case theelectrical resistance of the tissue R_(et) may be on the order of 4,800ohms. Based a primary impedance Z_(p)=100 ohms and a secondary impedanceZ_(s)=4,800 ohms, the transformer 172 should be a step-up transformerwith a turns ratio, N_(p)/N_(s) of 1:7. When the primary impedance Z_(p)is increased back to 300 ohms for a generator with this high impedancecut-off, the transformer 172 should be a step-up transformer with aturns ratio, N_(p)/N_(s) of 1:4.

Returning to FIG. 11, as indicated above the high impedance cut-off forbipolar mode at 75 watts occurs at about 300 ohms. Based on Ohm's law,for 75 watts and 300 ohms, the voltage before power begins to drop inbipolar mode is about 150 volts RMS (root mean squared). However, withuse of transformer 172, the voltage associated with the first and secondcoils are also changed along with the impedances. With the transformerabove, secondary voltage may be described as follows:V _(s) =V _(p)(N _(s) /N _(p))  (7)where:

V_(s)=Secondary voltage;

V_(p)=Primary voltage;

N_(p)=Number of turns (windings) for primary coil; and

N_(s)=Number of turns (windings) for secondary coil

With a primary voltage V_(p)=150 volts RMS as calculated above, and aturns ratio, N_(p)/N_(s) of 1:1.7, the secondary voltage V_(s) is equalto 255 volts RMS. However, with a primary voltage V_(p)=150 volts RMS,and a turns ratio, N_(p)/N_(s) of 1:5.8, the secondary voltage V_(s) canincrease to 870 volts RMS.

In certain instances, it may be desirable to decrease the secondaryvoltage V_(s) back to its “pre-transformer” level, in other words, forexample, 150 volts RMS. As shown in FIG. 27, device 10 may be providedwith an autotransformer 192, which, among other things, is a transformercomprising a single coil as opposed to two coils. As shown in FIG. 27,autotransformer 192 comprises a single coil 196 which is wound aroundcore 194 to produce, what is electrically, a primary and a secondarycoil. This is different from the conventional two-coil transformer 172,which has the primary and secondary coils 173, 175 electricallyinsulated from each other, but magnetically linked by a common core. Theautotransformer's “coils” are both electrically and magneticallyinterconnected.

The coil 196 is tapped at a location along a portion of its length bytap 198, which results in a voltage change which corresponds to thelocation of the tap 198. As shown in FIG. 27, the AC voltage from thesource (generator 136) is connected across many more turns on the singlecoil 196 than is the output connections for the electrodes. The coil 196has a specific number of volts per turn. By tapping up so many turns, alower voltage can be obtained. More specifically, the voltage change isdetermined by the turns ratio N_(p)/N_(s) corresponding to the locationof the tap 198.

Equally important in the use of autotransformer 192 is that, as shown inFIG. 27, the primary and secondary share a common connection. Sincethere is a direct connection between primary and secondary, theautotransformer 192 provides no isolation. Consequently, there issubstantially no resistance, if any, between primary and secondarycoils. This is the primary advantage associated with usingautotransformer 192. The voltage between the primary and secondary maybe substantially decreased, with no substantial change in the resistancebetween the coils. Thus, the resistance between the coils stayssubstantially the same, and the higher impedance cut-off created withuse of transformer 172 is maintained even though autotransformer 192 hasbeen added to the device 10 and the system.

For autotransformer 192, the secondary voltage V_(s) associated withtransformer 172 now comprises the primary voltage V_(p) forautotransformer 192. As a result, using the formula above, to bring aprimary voltage V_(p) of 870 volts RMS of the autotransformer 192 backto a secondary voltage V_(s) to 150 volts RMS, a step-downautotransformer is used with a turns ratio N_(p)/N_(s) of 5.8:1. Asshown, the autotransformer 192 has a turns ratio N_(p)/N_(s) which isexactly inverse to the turns ratio N_(p)/N_(s) associated withtransformer 172.

It should be understood that, while the voltage may be theoreticallyreturned to its “pretransformer” level with the use of autotransformer192, Ohm's Law, in addition to electrode geometry, tissue resistivity,device design, device method of use and system configuration, may imposeadditional practical limitations. For example, for a bipolar power of 50watts, and an electrical resistance of the tissue R_(et) on the order of4,800 ohms, Ohm's Law provides that the practical lower limit on voltageV_(s) is about 490 RMS to get an acceptable current flow. While this isgreater than the 150 volts RMS which normally may be observed with known“dry” bipolar devices, the devices of the present invention mayfacilitate the use of higher voltages without adverse consequences dueto, among other things, the presence of a fluid provided at the tissuetreatment site. Thus, it should be understood, that the turns ratioassociated with the respective transformers is merely exemplary, andthat the turns ratio N_(p)/N_(s) associated with the autotransformer 192merely be greater than the turns ratio N_(p)/N_(s) associated withtransformer 172 to obtain a decrease in voltage.

In other embodiments, it should be recognized that the relativepositions of the transformer 172 and autotransformer 192 may be reversedin series between the generator 136 and device 10.

Returning to FIG. 11, the output power is identified as being set to 75watts in the generator's bipolar mode of operation. With respect togeneral-purpose generators currently used in the electrosurgicalindustry, it has been found that a significant portion of the generatorsonly provide an output power of 50 watts in their bipolar mode, withonly a few providing an output power of 70-75 watts in bipolar mode.Above 75 watts, a very small number of generators may provide power intheir bipolar mode of 100 watts.

As is well known, the maximum output power of a general-purposegenerator in its bipolar mode of operation is lower than the maximumoutput power of the generator in its monopolar mode of operation. Onereason for this is that the electrodes commonly associated with abipolar device, such as device 10, are generally in much closer inproximity as compared to the active and return electrodes of a monopolardevice, thus reducing the need for greater power. Furthermore, withadditional power, use of many prior art dry tip electrosurgical devicesonly leads to more tissue desiccation, electrode sticking, charformation and smoke generation, thus further obviating the need foradditional power.

However, as established above, device 10 of the present inventioninhibits such undesirable effects of tissue desiccation, electrodesticking, char formation and smoke generation, and thus do not sufferfrom the same drawbacks as prior art dry tip electrosurgical devices.Consequently, it has been found that bipolar devices which provide powerand fluid to a treatment site may, in certain instances, be able to usesignificantly greater power than the output power currentgeneral-purpose generators offer in their accorded bipolar modes ofoperation.

General-purpose generators may offer significantly greater output powerthan 75 watts when set in their monopolar modes. For example, inmonopolar “cut mode”, the maximum power output of the generator istypically in the range of 300 watts. However, in monopolar cut mode, thevoltage and working impedance range are much greater than in bipolarmode. For example, an exemplary high impedance cut-off for a monopolarcut mode is about 1000 ohms. At 300 watts and 1000 ohms, the voltage inmonopolar cut mode is about 548 RMS. Furthermore, this voltage may beeven higher for generators with a high impedance cut-off above 1000ohms. For example, certain generators may have a high impedance cut-offin monopolar cut mode of about 3500 ohms at 150 watts. This correspondsto a voltage of about 725 volts RMS.

In order to reduce monopolar cut mode voltage to a desirable level forbipolar use, without correspondingly decreasing the high impedancecut-off, autotransformer 192 may be placed in series circuitconfiguration between the electrodes of bipolar device 10 and themonopolar mode power output of the generator 136.

With the introduction of a autotransformer 192 to convert monopolaroutput power voltages to voltages associated with bipolar output power,preferably the wires 36, 38, plug connectors 35 a, 35 b andautotransformer 192 are all assembled and provided in a single housing43 shown in FIG. 28, for similar advantages to those discussed inreference to FIG. 25.

FIG. 28 further illustrates an exemplary electrical configuration whichmay be associated between device 10 and generator 136. As shown in FIG.28, in this embodiment the wiring within plug housing 43 of device 10 isconfigured such that hand switch 142 a may be electrically coupled tothe monopolar “cut mode” hand switching circuitry of generator 136. Morespecifically, as shown hand switch 142 a is electrically coupled togenerator 136 upon the insertion of hand switch plug connector 35 g ofdevice 10 into hand switch receptacle connector 137 g of generator 136.

In other embodiments, the wiring within plug housing 43 of device 10 maybe configured such that hand switch 142 a is coupled to plug connector35 h and plug receptacle 137 h, in which case hand switch 142 a is nowelectrically coupled to the monopolar “coagulation mode” of generator136 rather than the cut mode.

In addition to plug connector 35 g, plug housing 43 also contains powerplug connector 35 e which may be electrically coupled to the monopolarpower receptacle connector 137 e of generator 136. As shown, uponinsertion of power plug connector 35 e into power receptacle connector137 e, electrodes 64 a, 66 a are now coupled to generator 136. Finally,as shown, the last connection of device 10 to generator 136 comprisesground pad receptacle connector 35 f being inserted over ground pad plugconnector 137 f of generator 136 to couple electrodes 64 b, 66 b togenerator 136.

In other embodiments, as shown in FIG. 29, the hand switch 142 a may beeliminated and foot switch 142 may be used alone.

In still other embodiments, the autotransformer 192 may be provided aspart of an electrical adaptor 200 provided in series between device 10and generator 136 as shown in FIGS. 30 and 31. In this embodiment,preferably the adapter 200 includes its own receptacle connectors 202 a,202 b on one side which are configured to receive plug connectors 35 a,35 b of device 10, and on the opposing side has its own plug connector204 e and ground pad receptacle connector 204 f which are configured toconnect to receptacle connector 137 e and ground pad plug connector 137f of generator 136, respectively.

As shown in FIG. 31, adaptor 200 may also be configured to accommodatedevice 10 with hand switch 142 a. In addition to the various connectorsidentified above, adaptor 200 has its own bipolar hand switch receptacleconnector 202 c on one side configured to mate with the bipolar handswitch plug connector 35 c of device 10, and on the opposing side hasits own monopolar hand switch plug connector 204 g configured to connectto monopolar “cut mode” hand switch receptacle connector 137 g ofgenerator 136. Finally, in order to establish the remaining link betweenthe hand switch circuitry and the bipolar power output, the adaptor 200has a hand switch plug connector 202 d configured to mate with handswitch receptacle connector 35 d of device 10.

As shown in FIG. 31, device 10 now includes four connectors (i.e. 35 a,35 b, 35 c, 35 d) when adaptor 200 is used rather than just the threeconnectors (i.e. 35 e, 35 f, 35 g) associated with FIG. 28. Connector 35d is added to provide a connection, when mated with connector 202 d ofadaptor 200, to plug connector 204 e which bypasses autotransformer 192.

Turning to the specifics of autotransformer 192, similar to transformer172, preferably coil 196 of autotransformer 192 comprises #18 magnetwire wound on a toroidal shaped, magnetic core 194. More preferably thecore 194 comprises a ferromagnetic core and even more preferably aferrite core. Preferably the ferrite has an amplitude permeability inthe range of 500μ to 5,000μ and more preferably of about 2,000μ. Morepreferably, the ferrite comprises ferrite material no. 77.

With autotransformer 192 above, similar to equation (7), secondaryvoltage may be described as follows:V _(s) =V _(p)(N _(s) /N _(p))  (8)where:

-   -   V_(s)=Secondary voltage;    -   V_(p)=Primary voltage,    -   N_(p)=Number of turns (windings) for primary coil; and    -   N_(s)=Number of turns (windings) for secondary coil (i.e. number        of turns to the tap)

Using the formula above, to bring the primary voltage V_(p) of 725 voltsRMS down to a secondary voltage V_(s) to 150 volts RMS, a step-downautotransformer is used with a turns ratio N_(p)/N_(s) of 4.8:1.However, as explained above, the devices of the present invention mayfacilitate the use of higher voltages without adverse consequences, dueto, among other things, the presence of a fluid provided at the tissuetreatment site.

For purposes of the appended claims, the term “tissue” includes, but isnot limited to, organs (e.g. liver, lung, spleen, gallbladder), softtissues including highly vascular tissues (e.g. liver, spleen) andtissue masses (e.g. tumors).

While a preferred embodiment of the present invention has beendescribed, it should be understood that various changes, adaptations andmodifications can be made therein without departing from the spirit ofthe invention and the scope of the appended claims. The scope of theinvention should, therefore, be determined not with reference to theabove description, but instead should be determined with reference tothe appended claims along with their full scope of equivalents.Furthermore, it should be understood that the appended claims do notnecessarily comprise the broadest scope of the invention which theApplicant is entitled to claim, or the only manner(s) in which theinvention may be claimed, or that all recited features are necessary.

All publications and patent documents cited in this application areincorporated by reference in their entirety for all purposes, to theextent they are consistent.

1. A fluid-assisted tissue grasping device comprising: a first jaw and asecond jaw, at least one of the jaws being movable toward the other jaw;the first jaw having a first jaw tissue grasping surface and the secondjaw having a second jaw tissue grasping surface, the tissue graspingsurface of each jaw directly opposing each other and comprising anelectrically insulative surface; a first electrode and a secondelectrode, the first and second electrodes configured to have oppositepolarity when electrically coupled to a radio frequency power source andpositioned for an electrical current from the first and secondelectrodes to flow in tissue grasped between the tissue graspingsurfaces substantially parallel to the tissue grasping surfaces andacross a width of the tissue grasping surfaces, the first jaw tissuegrasping surface and the second jaw tissue grasping surface being medialto the first electrode and the second electrode, and the first electrodeand second electrode being laterally outside the first jaw tissuegrasping surface and the second jaw tissue grasping surface so that thefirst electrode is separated from the tissue grasping surfaces by afirst gap for fluid and the second electrode is separated from thetissue grasping surfaces by a second gap for fluid; at least one fluiddelivery passage; and at least one fluid outlet to receive fluid fromthe fluid delivery passage and to deliver the fluid to the first andsecond gaps.
 2. The device of claim 1 wherein: the at least one fluidoutlet further comprises a first fluid outlet and a second fluid outlet.3. The device of claim 2 wherein: at least one of the first fluid outletand the second fluid outlet is used to provide a fluid onto the firstelectrode or the second electrode, respectively.
 4. The device of claim2 wherein: at least one of the first fluid outlet and the second fluidoutlet is at least partially defined by the first electrode or by thesecond electrode, respectively.
 5. The device of claim 2 wherein: thefirst jaw tissue grasping surface has a first edge opposite a secondedge; and at least one of the first fluid outlet and the second fluidoutlet is used to provide a fluid between the first electrode and thefirst edge of the first jaw tissue grasping surface or between thesecond electrode and the second edge of the first jaw tissue graspingsurface, respectively.
 6. The device of claim 2 wherein: the first jawhas a first side portion opposite a second side portion; the firstelectrode being on the first side portion of the first jaw; the secondelectrode being on the second side portion of the first jaw; the firstfluid outlet is on the same side portion of the first jaw as the firstelectrode; and the second fluid outlet is on the same side portion ofthe first jaw as the second electrode.
 7. The device of claim 2 wherein:the at least one fluid delivery passage comprises a first fluid deliverypassage and a second fluid delivery passage; the first fluid outlet influid communication with the first fluid delivery passage; and thesecond fluid outlet in fluid communication with the second fluiddelivery passage.
 8. The device of claim 7 wherein: at least a portionof one of the first fluid delivery passage and the second fluid deliverypassage is defined by the first electrode or the second electrode,respectively.
 9. The device of claim 1 wherein: at least one of thefirst electrode and the second electrode comprises a hollow structure.10. The device of claim 1 wherein: the tissue grasping surface of atleast one jaw comprises a hydrophobic surface.
 11. The device of claim 1wherein: the tissue grasping surface of at least one jaw has one or moreserrations.
 12. The device of claim 1 wherein: the first jaw comprises afirst jaw support structure beneath the first jaw tissue graspingsurface, the first jaw support structure having a first side portionopposite a second side portion; the first electrode being along thefirst side portion of the first jaw support structure; and the secondelectrode being along the second side portion of the first jaw supportstructure.
 13. The device of claim 1 wherein: at least one jaw comprisesa support structure beneath the tissue grasping surface; and the supportstructure provides a heat sink for transferring heat away from thetissue grasping surface.
 14. The device of claim 1 further comprising:at least one stand-off overlying at least a portion of one of the firstelectrode and the second electrode, the stand-off to inhibit tissue fromphysically contacting the electrode.
 15. The device of claim 1 furthercomprising: a tissue treatment indicator which provides an outputrelated to the level of treatment of tissue.
 16. The device of claim 1further comprising: a cutting mechanism.
 17. The device of claim 1,wherein at least a portion of each of the first and second gaps isconfigured to receive a portion of a fluid expelled from the fluidoutlet therein.
 18. The device of claim 17, wherein at least a portionof each of the first and second gaps is configured to provide a fluidflow channel for the fluid along a length of the tissue graspingsurfaces.